The word blog is short for Weblog.
A weblog is something like an online diary. Any registered user can create one, either by entering text or HTML into a form, or by clicking the small pushpin icon next to a listing in a box that contains a newsfeed item or a forum thread.
The user blogs area of the site allows you to view the weblogs of other users.
Unlike other kinds of content, blogs are posted to the site and visible by other users immediately.