This is an alternative blog that you can install into standard Moodle.
It does not replace the standard blog, and operates alongside it. There are two modes of use:
1) As a course activity. In this case you can use it the same way as any other module. You can have course-wide blogs (everyone in the course posts to the same blog), group blogs, or individual blogs; the latter are useful for assessed activities (where the student is supposed to keep a journal which only they and their tutor can read).
2) As a replacement for standard Moodle personal blogs. In this case it would be a good idea to turn off the standard Moodle blog system, or it'll bevery confusing. You then need to MANUALLY provide students with a link to mod/oublog/view.php which will automatically take them to their personal blog.
When using for personal blogs, one feature of interest may be moderated public comments; when you allow comments from people who are not logged in, all such comments are moderated.