Facebook is a social networking service and website launched in February 2004, owned and operated by Facebook, Inc.As of May 2012, Facebook has over 900 million active users, more than half of them using mobile devices.
Twitter is an online social networking service and microblogging 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 140 million active users as of 2011
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 HTML5 technology 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.