Twitter

Twitter is an online social networking service and microblogging service that the users can send and read text-based posts, known as "tweets". 
Twitter messages are public but users can also send private messages.
Twitter has been used for a variety of purposes in many different industries and scenarios. For example, it has been used to organize protests, sometimes referred to as "Twitter Revolutions" and which include the 2011 Egyptian revolution.

We can access it from this address: http://twitter.com/

@JliaLloansi