Supposing I want to send someone a URL to one of the pages of my site. Then if the URL is too long it gets complicated. In emails there's the risk that the long URL gets broken up on many lines. And on SMS there's too much typing. So I've introduced Quick URLs.
For example: http://www.peterbe.com/photos/misc/balloon-flying/ballong_skog_eld.jpg/view becomes http://www.peterbe.com/q-004 Much easier to type in when sending a text, isn't it.
I have to manually select every URL that I want to do this too, but this might change with time. When you enter a Quick URL like the one above you get redirected to the real URL.