A blog consists of individual's posting on any topic of his or her choosing.  It could be an opinion, information, an observation, or just a statement to be made.  I've only read blogs, but the ones I saw were so negative that I stopped reading.  A blog can be used in encouraging writing, expressing opinion or interpretation, or instructing other students on a topic.  https://www.blogger.com/blogger.g?blogID=1256059005963616367#editor/target=post;postID=7678439071551956877