Twitter is a messaging service that shares a lot of characteristics with communication tools you already use. It has elements that are similar to email, IM, texting, blogging, RSS, social networks and so forth. But a few factors, particularly in combination, make Twitter unique:

Messages you send and receive on Twitter are no more than 140  characters, or about the length of a news headline. That means they’re really easy to write and read.

Messages on Twitter are public, like blog posts, and you don’t have to give people permission to see what you’ve written. That means you can readily meet new people on Twitter.

The messages are opt-in, and people choose to get a stream of others’ messages. (On
Twitter, this model is called “following.”) That means you have to be interesting, or
people will choose not to get your updates.

You can send and receive the messages via a variety of mechanisms, including mobile
phones, PCs, websites and desktop programs, and they’re distributed in real time. That
means that Twitter can fit with nearly anyone’s workflow.

When you add all that together, and you throw in a dose of the friendliness common on
Twitter today, you get a powerful and appealing communications platform that turns out to
be highly useful for a slew of personal and professional needs.