The number is the number of the post; it's also an anchor in the page. The text before .html is the subject line; when you access a child post of a parent topic it will link you to the thread of the parent topic with the anchor of the post defined...
So, you access 226059 it loads the thread starting with topic 226056 and "anchors" you to 226059.
Why do they display duplicate content? Well, it's the same thread... page=1 would also link you to duplicate content...
