WordPress did a video tour of WordPress 2.6 to help you understand the new features:
What’s new in WordPress 2.6?
Post revisions — ever miss the editing records of your blog post? WordPress 2.6 now included the wiki-like tracking for blog edits. It allows you to view who made what changes when to any post or page through a super-easy interface.
Blogging bookmarklet — drag the “Press This” bookmarklet to your browser’s bookmark bar. Then, whenever you see something interesting to blog about, just click on the bookmarklet. It will load a minimized version of WordPress editor which allows to blog different content: text, photo, quote, and video, instantly. It is very much like the Tumblr and allows you to create a tumbleblog-like mini blog site.