Blog is a short form version of the words "web log". As is typical of on line terminology, it can rapidly change from its origin into something that is not understood unless you happened to be there when it changes, or are exposed to it. For other definitions like these you can check out ....
And here is what they say a blog is....
a.k.a. blogger -or- blogrolling -or- weblog -or- Web log
A Web site (or section of a Web site) where users can post a chronological, up-to-date e-journal entry of their thoughts. Each post usually contains a Web link. Basically, it is an open forum communication tool that, depending on the Web site, is either very individualistic or performs a crucial function for an organization or company.
Part of the appeal of blogging is that the programs you use to publish your insights on the World Wide Web are easy-to-use and you do not have to be a programmer, or even know how to code.