Well twitter is a microblogging service. You post in under 140 characters and tell the world what you're doing. You follow people to see what they're doing, and people follow you to see what you're doing. Lots of followers is a good thing.
When you enter what you're doing it's called a "tweet" and if someone's already said it it's called a "retweet"....the more retweets we have on our topics the better because people click the links to come view the topic
. Even if a topic has 100 tweets, they might not have been recent!