Difference between a Blog and regular Writing?

I've been doing some reading on Blogs, thinking it would be an interesting hobby to partake in, but disagree with the methods many articles seem to push people in.

If I were to take up writing, and write about things that I have gone through, or things I enjoy, or even just writing about something I'm passionate about, is it or is it no longer a blog. I know many blogs are focused on an individual thing/s, or more specifically things people want information on. What is the difference between a Blog and regular Writing?