Twitter is social network and microblogging platform founded in 2006. As of 2016 Twitter has 319 million active users.
Along with Facebook and Google+, Twitter is one of the most important social media marketing platforms. It allows direct interaction and engagement with your customers and audience. And while links posted on Twitter do not pass link juice, Google does follow them, so posting links on Twitter can be a good way to get pages indexed.
For businesses, Twitter also offers an analytics platform to measure marketing performance.