The word 'blog' is a contraction of 'web log'. Blogs are a form of online journal used by millions of people around the world for self-expression and communicating with family and friends. Blogs are usually organized as a chronological series of postings created by the author of the blog. Blogs usually are written by one person, although some blogs can be authored by groups of people.
Blogs in Moodle are user based - each user has their own blog. Users can also register their external blogs, such as Blogger or Wordpress, so that entries are automatically included in their Moodle blog.