A blog is an online journal, diary or news column with options for readers to comment.
Blogs in Moodle are automatically set up as part of a user's profile; it is user-specific, not course specific. You can also create user blogs or a course blog as an activity within a course. Users can also register their external blogs, such as Blogger or WordPress, so that entries are automatically included in their Moodle blog.
For more information, please visit the following UNSW Learning and Teaching page: Blog in Moodle.