Facebook ( own spelling : facebook ) is a social network operated by the American company Facebook Inc. of the same name . The company had sales of $ 41 billion in 2017 .
Facebook enables the creation of private profiles for representing yourself, company pages for business presence, and groups for private discussion of common interests. The profiles can be networked through friendship requests, whereby an unlimited number of subscribers (analogous to followers on Twitter) is possible, but the maximum limit of directly connected friends is limited to 5000 friends. In addition, Facebook offers a messenger and a development platform for creating application software .
The network, founded in 2004, claims to have around 2.23 billion members in the second quarter of 2018, who visited the site at least once a month.  According to Alexa , Facebook is ranked 3rd (2015: 2) and 6th (2015: 3) of the most visited websites worldwide in the fourth quarter of 2016 and according to other statistics recorded 30 million active users in Germany in May 2017.
Since its publication, Facebook has been criticized for inadequate data protection practices , particularly by European data protection and security experts.  The Federation of Consumer Organizations in Germany advised in 2010 even from getting to use the service. 
Facebook’s growing importance as a news channel was documented by the Reuters Institute at Oxford University in 2015 . According to this, 23% of 1,969 respondents across Germany from all age groups received their messages from Facebook. In the USA, the corresponding figure was 41% of 23,557 respondents.   According to a long-term study by TU Darmstadt and TU Dresden , in 2014 around 91 percent of all online news from media companies in Germany were disseminated via the Facebook Like and Share buttons .   The problems include the spreading or lack of containment of false reports ( fake news ) in the network and the effect of its filter bubble , a narrowing of the information width through automatic selection.
Developed in 2003 , Mark Zuckerberg , the site facemash.com , the predecessor to Facebook, during his studies of psychology and computer science at Harvard University . It was a public appearance rating system for women that only lasted a few days due to protests. Zuckerberg posted photos of female students on the Internet without their permission and asked visitors to choose the more attractive from two randomly selected photos.
Facebook in its current form has existed since spring 2004. In Harvard, the web-based version of the official, printed yearbooks was slow to get going due to privacy concerns . The expanded concept first spread through the Ivy League universities and then worldwide. The platform reached around 800 million members worldwide in September 2011. In addition to Mark Zuckerberg , the students were Eduardo Saverin , Dustin Moskovitz and Chris Hughes involved in the project. In 2004 Napster’s co-founder , Sean Parker, also rose, joined the team as a consultant and received a seven percent stake in Facebook. After Parker was arrested for possession of cocaine , he was forced to leave Facebook.
The company Facebook Inc. there since 4 February 2004. The announced 2 February 2012  initial listing on the stock exchange was put into effect on 18 May 2012 found.  In the first week after the IPO, the share price fell from 38 to around 33 dollars. The stock exchange regulator accused Facebook of withholding information from small investors. These brought class action lawsuits for damages.
On February 19, 2014, Facebook Inc. bought the WhatsApp messenger service for $ 4 billion in cash and $ 15 billion in Facebook shares. As part of the sale, WhatsApp co-founder Jan Koum moves into the Facebook board of directors.
On March 25, 2014, Facebook Inc. announced the acquisition of Oculus VR . Oculus VR was acquired by Facebook for a purchase price of $ 400 million in cash and $ 1.6 billion in Facebook shares.
In December 2015, Facebook founder Mark Zuckerberg announced that he would sell 99% of his Facebook shares. On August 23, 2016, the Facebook boss sold the first share package worth the equivalent of 95 million euros to support the Chan-Zuckerberg initiative with financial resources. The sale did not affect the company’s share price.  However, it is doubted that this is a real donation, because the Chan-Zuckerberg initiative is not a real foundation, but a limited liability company . This enables Zuckerberg to keep taxes down and to present himself as a benefactor in the media.
In the spring of 2018, the company increasingly came into the public eye after the 2016 United States special campaign to influence the election campaign found that agents of the Russian Federation had used Facebook to a greater extent to influence the US presidential election campaign. In this context, it was announced that the company Cambridge Analytica the data of up to 87 million gives Facebook users had.
Every Facebook user has a profile page where they can introduce themselves and upload photos and videos. This page is available at www.facebook.com/your username . Visitors can leave publicly visible messages on the profile or post comments on their own contributions from the profile owner. However, Facebook became famous for its Like or Like button, with which users can express their opinions with just one click if they approve of something. As an alternative to public messages, users can send or chat personal messages . For common areas of interest, so-called groups and friends can be invited to events . Facebook also has a marketplace where users can post and view classified ads. 
The identity of newly registered users is only checked using the email address. In October 2010, an employee of the news magazine TechCrunch reported that he had created an account on Facebook with the name of Google manager Eric Schmidt using his correct email address . Since Facebook accounts that have not yet responded to the confirmation message already allow certain actions, such as setting up the profile and sending private messages, Eric Schmidt’s fake account received private messages from various acquaintances who apparently believed the account to be real. 
Until 2012, the profile page was the home page on Facebook. In order to see all the activities of his friends, you had to go to the respective profile page of the friend individually. With the introduction of the news feed, this information was automatically displayed on the start page.
Profile and history
On 16 December 2011, the function was Chronicle ( English timeline ) enabled.  The user should be able to present his life chronologically or to keep a kind of diary. While the chronicle could initially be optionally activated by users, it has been mandatory since autumn 2012 and is also forcibly activated on older accounts as a Facebook homepage.  All messages from the user also appear here, whereby the user can choose who can see them.
Facebook not only provides profiles for individuals , but also so-called pages ( English Facebook Pages ) for artists, famous people, companies and brands.  In contrast to the profiles of members and contributions from groups, pages are also visible to users who are not logged in to Facebook. The following page categories are distinguished:
local business or location;
Company, organization or institution;
Brand or product;
Artist, band or public person;
good cause or community.
Facebook pages are often used as part of social media marketing or public relations activities. Generally, the more emotional a product or service is, the easier it is to acquire fans on Facebook.
Selected advertising customers (so-called Facebook Business Partners ) have had the opportunity since October 2012 to combine several pages under a single address and a uniform dashboard with a “global page” . Depending on the language and location, the visitor is then shown the relevant content. 
A location structure can be requested for companies with multiple physical locations. The Facebook pages of the individual locations are subordinate to the main page and can take over content and user roles from the parent page, but also individually assign rights and share content. Contact details and opening times can be set for each location and users are shown a map of locations in their vicinity.
Every user can set up groups on Facebook, for example to discuss a topic, similar to an Internet forum . A group can be created publicly (visible to everyone), closed (posts are only visible to members) or secret , whereby the existence of the group remains hidden from others. It can be determined that new members are accepted immediately, only after confirmation by an administrator or after confirmation of each member.Furthermore, you can set whether new contributions from members are either immediately visible to everyone or only after activation by an administrator or moderator. Many groups were created to discuss current affairs in a city, to sell or give things away. There are some different functions within the group compared to general use. This is what a group administrator seesevery registered member – even if he has been banned from it. All other group members, on the other hand, can only see the profiles and discussion contribution if the respective participant has not blocked the other. Several administrators and moderators can be set up for a group, which can be an advantage for very large groups if, for example, membership requests have to be processed.
Facebook has had a search function from the beginning to find new friends or groups. On January 15, 2013, Mark Zuckerberg introduced the newly designed Facebook Graph Search .  In contrast to the previous solution, it is a semantic software that can interpret and understand conditions instead of just keywords as before .  Facebook wants to answer queries such as Find all friends who were in Berlin yesterday. Graph Search is currently in betaavailable to users using Facebook in English. This only supports people, photos, places and interests. Further content (contributions, comments, events) and languages should follow.
Since June 2013, Facebook has also been able to use hashtags .According to the developers, these should make the search easier, especially in the case of current content. This also includes so-called trending hashtags , which are particularly often given in your own circle of friends.
From 2008 to 2013, Facebook offered its own currency based on the model of Second Life , the units of which are called Facebook Credits . The virtual currency could be acquired using various methods, for example by credit card . It could be used for all commercial applications and games on Facebook, but could not be exchanged for real money.  With each transaction, Facebook withheld part of the amount, which initially amounted to 30 percent. The virtual currency could also be accepted from offers outside the social network via the Facebook API . Facebook resumed its own virtual currency on September 12, 2013, and has since switched back to local currencies in APIs.  In 2019, Facebook founded Libra Networks in Geneva . Since then there has been speculation about the introduction of an online payment service .
Under the name Facebook Messenger there is an application for text and audio communication for the operating systems iOS and Android . It is integrated with Facebook’s web chat function, but can be used independently as an app. Technically, it is based on the open MQTT message protocol . 
In cooperation with Skype , Facebook presented a function on July 6, 2011 under the motto “Sometimes emoticons are simply not enough”, with which users of the network can conduct a video conference if they have a webcam . The conversation took place directly in the browser, an additional application was not necessary. Only a plug-in had to be installed.  In the course of the cooperation, the possibility was also created to automatically view contacts from Facebook in Skype. News from the network were also presented. Members of the social network were also able to log in to Skype without registering again. 
In January 2013, Mark Zuckerberg announced that at least the iOS version of the Facebook messenger now supports phone calls. These are implemented as Voice over IP and are free of charge. This service is now also available for Android and in other countries, including Germany.
In November 2014, the company reported 500 million,  in July 2016 of a billion users. 
On April 28, 2015, Facebook launched its own free video call function via Messenger in competition with Skype and Facetime , which was initially available in 18 test countries (excluding Germany) and later worldwide.
→ Main article : Facebook Watch
Facebook Watch is a video-on-demand service from Facebook for series, shows, documentaries, and user videos that was launched on August 9, 2017. The service is available on mobile devices, computers and in the Facebook TV apps . Users should interact more socially with the videos, for example by looking, rating, commenting and seeing what the other users are saying.
Facebook Safety Check
Safety Check is a function activated by Facebook in the event of disasters and similar events, by means of which relatives or other potential victims can be informed as quickly as possible that the person concerned is safe. The activation of this function is now perceived by the media as a characteristic of catastrophes or other serious events such as terrorist attacks.