A blog or weblog is basically a website that is similar to an online journal with links and postings. Materials are posted with the most recent comments appearing at the top of the page.
Check out this video: Blogs in Plain English
If you want to make a blog, you can create one in SchoolCenter or use one of the other hosting services such as Word Press or Edublogs.
INFORMATION AND SAMPLES BLOG HOSTING SERVICES Blogs in Education Edublogs Blog Basics WordPress Book Blog Class Blogmeister Scott McFarland's 5th Grade Blogs