Share Web 2.0

Web 2.0 is occasionally thought of as a buzz word by many people.

See the original post:
How Can You Benefit From Web 2.0? | Youtube Marketing Coaching

Apparently there’s a lot of discussion and whatnot regarding the definition of the word “blog.” As I understand it, a “blog” is a webpage with the users thoughts regarding a certain subject or topic of interest.
Is that about the right definition?
How do you define the word “blog?”
Furthermore, what do you consider an online diary or personal journal? Do these count as “blogs” or are they something else entirely?
I always associate my webpage (personal journal) with “blog” but I don’t think it fits the definition I listed above since all it really is is an account of my day-to-day life.