It's often called a social network or a microblogging service, but it's really just an instant messaging service on steroids.
At its core, Twitter is about sending and receiving group messages. The messages are limited to 140 characters and they are called tweets. It has many add-ons that make it powerful, but text messages are the real answer to the what is Twitter question.
Twitter as Social Network and a Microblog
Twitter also is considered a social networking service because people create profiles and connect with other people electronically on the service. The connecting process is similar to Facebook, only on Twitter the people who connect with you are called "followers" instead of "friends." As with Facebook, you develop a list of connections whose profiles you can browse and with whom you can swap messages.
The reason some people also call Twitter a "microblogging" service is because they think of Twitter as a miniature blog, even though the two are really very different things. Twitter messages or tweets are shorter than a typical blog post, hence the "micro" description. But they are somewhat similar to blog posts in the sense that tweets are meant as information updates that people can subscribe to, just like blog posts.
Still, it's best to think of Twitter as its own thing, and what Twitter is amounts to a social messaging service.
Why Do People Use Twitter?
People use Twitter to learn about topics they care about and to share their thoughts with other people--in other words, to both send and receive messages.
After the service launched in 2006, it quickly became a major communication platform for news and information, used both professionally and personally. Millions of people use it to keep up to date on news and trends in their professions or areas of interest, simply by reading tweets.
Celebrities and media professionals are big Twitter users, sending tweets out to legions of followers. Politicians and government officials also send many tweets, which often are quoted in the media as sources of news.
Because Twitter is a two-way messaging system, most Twitter users also choose to communicate their own thoughts and ideas by writing and sending tweets to their followers. Those followers can include friends, professional colleagues, others working in the same field, members of other niche audiences, and even the general public.
Why Do Companies Use Twitter?
Businesses of all kinds also use Twitter to market their products and services, and to engage in dialogue with their customers.
After Figuring Out What Twitter Is, What's Next?Ok, Twitter is a short messaging service, but what else does it do?
Unlike traditional instant messaging apps, Twitter by default publishes all of your tweets in a public timeline that anyone browse. You can make your tweets private, but that severely limits the usefulness of your Twitter account.
If people can't browse your tweets because they're private, fewer people will be able to "follow" you, and Twitter is all about people "following" or text-talking to other people.