What exactly is Twitter? Liz Lawley explains it best:
Twitter is a site that allows you to post one-line messages about what you’re currently doing—via the web interface, IM, or SMS. You can limit who sees the messages to people you’ve explicitly added to your friends list, or you can make the messages public.
Think of it as a blend of blogging and instant messaging. Recipients of the information need not be online to receive your update, like they do in instant messaging, and previous updates can be read, like in blogging.
My first thought, like yours, is probably "who wants that kind of information?" I certainly don't need (or want) to know what my fellow Know More Media bloggers are doing at every moment. On the other hand, it would be nice to see what my husband is up to. He is a landlord and active in local politics, which means he spends his days running all over the place. We usually connect several times a day with a "what are you doing" phone call. Twitter is a faster, more efficient way of conveying that information to people who need it.
In a business setting, delivery personnel could use Twitter to alert he main office of deliveries or delays, without multiple phone calls. People working on a deadline could immediately communicate the completion of a task.
At first I was a little suspicious of Twitter, but now I can see the use of it - especially within a closed, very targeted network of "need to know" people.