So what is a blog? Blogs share ideas, report personal thoughts on different subjects and can be very useful. At the next couple websites you can look to see how Blogs are used.
http://oit.montclair.edu/documentationpdf/what_is_blog.pdf
This site teaches you to set up a blog at blogger.com.
http://codex.wordpress.org/Introduction_to_Blogging
This site describes the differences between a blog and a course management system.
Read through both to discover the pros and cons of blogging.