The App Store, much like its iOS counterpart, will seek to help surface, organize, and sell Mac software in an environment familiar to iTunes and iOS users. It will be used for installing, updating, and managing ownership of applications and games, as well.
It will be interesting to see what kind of applications and games show up on the App Store. It will certainly help independent developers get their app out there, but will we see the likes of Microsoft releasing the full Office suite through the App Store? What about high-profile games, especially now that Steam is up and running on the Mac?
Of course, the Mac App Store will be subjected to the same approval process in place on the iOS App Store as well as the same 70% / 30% split of revenue between the developer and Apple. In any case, I'm excited about having a digital storefront for applications on my Mac laptop. What about you?