What is a blog?
"Blog" is an abbreviation of the term "weblog". A blog is a system which allows non-technical people to easily and quickly add information to web pages.
Blogs allow just about anyone to put what they want to on the web, this is what makes them so interesting and so powerful. It is also why the have taken off in such a big way.
Many blogs focus on a particular topic; personal anecdotes, sports, technology, relationships, politics, state of the world etc...
The topics in any particular blogs can be very narrow and specific or very wide ranging. Personal blogs written like an online diary are very common.
A blog is usually updated frequently
A blog is just about anything the blogs creator wants it to be.