Twitter is technically a "micro blogging service"... but that does not really do it justice.
To describe twitter simply, it would go something like this. Twitter is a mechanism for people to distribute short pieces of text (140 chars) to people who have elected to be on their list.
Text communiques are known as "tweets" and people who receive them are "followers".
So then, what is the big deal?
The key difference is that for me to follow someone I do not require their permission. Unlike facebook where in order to receive status updates from people both sides need to agree.
So I could therefore follow Oprah Winfrey or Ashton Kutcher, or even Hugh Jackman.
So if you want to know what your hero is doing/thinking/wanting to tell the world... then why don't you look them up on twitter and follow them. You'll not only know what they're thinking about what you're interested in, you'll also probably know when they come back from a cycle.
Oh and btw, you can find me on twitter.