What are blogs?

Yahoo states in their article defining the blog, or weblog phenomenon,

"Weblogs and online journals are often confused, and they can frequently overlap in content and style. But purists point out that a person writing in an online journal or diary is logging their life, not the Web. Weblogs still exist to log what's going on around the World Wide Web."

I am puzzled... so this thing that I am writing... is actually just an online journal, but not a weblog/blog? Hm.