Twitter is basically a site where you can "follow" (not in a stalking sense, but you never know) other people, friends politicians, political parties, and now RCU. Twitter makes it really easy to post to your twitter (called a tweet) where your friends or others who are following you get that message, web page link, video etc. It makes it really easy for your message to get out to a group of people all at once. Hence Obama's use of twitter during the election. Many celebrities have their own twitter where fans can catch up with the latest that thier idols are doing. Basically you give people your twitter address, people follow you, and from then, they get all your tweets. Some people follow hundreds or thousands of people.

Tim