What's the "Combo" OS X Update? What's the difference between the OS X Mountain Lion Update v10.8.5 and the OS X Mountain Lion Update v10.8.5 (Combo) packages?

I'm running OS X 10.8.4
Combo Update allows you to update from whichever Mountain Lion version you’re using. It means you can update from v10.8.1 to v10.8.5 immediately.

While OS X Mountain Lion Update v10.8.5 means you can only update from the previous version, which is only OS X 10.8.4.