YouTube is a video-sharing website, created by three former PayPal employees in February 2005, on which users can upload, view and share videos.
The company is based in San Bruno, California, and uses Adobe Flash Video and HTMLtechnology to display a wide variety of user-generated video content, including movie clips, TV clips, and music videos, as well as amateur content such as video blogging and short original videos. Most of the content on YouTube has been uploaded by individuals, although media corporations including CBS, BBC, VEVO, and other organizations offer some of their material via the site, as part of the YouTube partnership program.
Unregistered users may watch videos, and registered users may upload an unlimited number of videos. Videos that are considered to contain potentially offensive content are available only to registered users 18 years old and older.
In November 2006, YouTube, LLC was bought by Google Inc.
Vimeo is a social networking of Internet on which users can upload, share, and view videos. It was founded by the company InterActiveCorp (IAC) in November 2004. Users have to be registered to upload videos, avatars and create its profiles and favorite lists.
Facebook is a social networking service and website launched in February 2004, operated and privately owned by Facebook, Inc. As of July 2011, Facebook has more than 800 million active users. Users must register before using the site, after which they may create a personal profile, add other users as friends, and exchange messages, including automatic notifications when they update their profile.
Facebook was founded by Mark Zuckerberg with his college roommates and fellow students Eduardo Saverin, Dustin Moskovitz and Chris Hughes.
A January 2009 Compete.com study ranked Facebook as the most used social networking service by worldwide monthly active users.
Twitter is an online social networking service and micro blogging service that enables its users to send and read text-based posts of up to 140 characters, known as "tweets". It was created in March 2006 by Jack Dorsey and launched that July.
The service rapidly gained worldwide popularity, with over 300 million users as of 2011, generating over 300 million tweets and handling over 1.6 billion search queries per day. It has been described as "the SMS of the Internet."
