A blog is like a diary, but usually topical.  So you could provide your perspective on, say, development.  Bloggers usually post frequently, writing short things -- something they spotted in the news (with a link to read more), a thought that has occurred to them, etc.

Think of it as a journal that is updated frequently with little bits of information.  And it's a journal where you'll get public feedback.

The best blogs are full of information, have their own personalities and can attract a following, but some people blog about their lives, which is usually not too interesting.

If you want to try it, at the lower right of the page, among your account links, is a link that lets you start a blog.

If you have questions or suggestions about this topic, add them below as a comment.