Twitter is microblogging - a place where teachers can share thoughts/resources in short "bites". Watch the famous Common Craft video tutorial, to get an idea of what twitter is all about. Also, this really simple - Mother, this is what twitter is all about
review.
Many great teachers "tweet" and send information. See some examples on this page I built. Barbara Sakamoto has a nice list of English Language Teachers you can start following immediately, once you set up your twitter account. Use this pdf tutorial which clearly outlines how to get started! Here's a video tutorial. Also worth a look: Can twitter make you a better teacher?
Twitter is a wonderful way to build community as a professional, gather ideas and resources, keep informed about conferences and events and just build a wonderful PLN (Personal Learning Network). Follow me at http://twitter.com/ddeubel
You might even get your students "tweeting" in a secure environment as a way to practice English! Use Twiducate. Students nowadays are social learners!