What you're reading right now is a post on the Zujava blog. We update this blog continuously with new content, a few times a week. That's the nature of a blog - to be updated often.
Blog posts are often shorter (not all the time), and to the point. Generally speaking, they have less images, less media, and sometimes have an expiration date of how relevant they are.
A leaf, on the other hand, is like a longer blog post that goes into further detail, and can include multiple forms of media to illustrate a point. It usually isn't updated as regularly as a blog, but can include updates and edits to make it more relevant for today. Instead of writing an entire new leaf on the same subject, you'd just edit the leaf to make it timely and updated.
Blog posts rarely get updated. They are static, but the blog itself -- which is a collection of blog posts -- will be updated with new posts.
What's the advantage of having a leaf over a blog post? Blogs will always have their place, but a leaf can become a go-to source for any one topic. You can mention all of the particulars and go off on extravagant detail on a leaf. The multitude of different sections Zujava offers like the YouTube, flickr, and Photo Block sections really add to the user experience, and make it simple for the author to do so.
Do you have more questions about the difference between a leaf and a blog? Ask away in the comments!
Intro photo by Cynthia Closkey on flickr, licensed under Creative Commons 2.0.