Twitter is an extremely popular micro-blogging service and social network that lets you follow and be followed, either publicly or privately, and share status updates in short tweets.
Twitter was created by Jack Dorsey, Evan Williams, Biz Stone, and Noah Glass in the late spring of 2006 and was initially used by people in the tech industry to stay in contact during and between conferences. Since SMS was a big part of its initial design, Twitter limited posts to fit inside the 160 character SMS limit of the time, reserving 20 characters for the username. When the iPhone launched, Twitter seemed like a perfect match and apps like Twitterrific not only helped take the service mainstream but contributed such foundational elements as the bird symbol and the word tweet. Twitter eventually acquired Loren Brichter's Tweetie apps, turned them into Twitter for iPhone, iPad, and Mac, and began launching additional apps for other systems.
Twitter has remained independent and has experimented with both internal diversification, like Twitter Music, and acquisitions, like Vine. Twitter is also currently integrated into both Apple's mobile and desktop operating systems, iOS and OS X.