Among the new features included is a new finder that let's you view more content in one windows thanks to tabs. Tags for files and Folders make it easier to organise as well as find files and documents. The Maps and iBooks app which was originally only for iOS devices is now included in the new Mac OS. Software improvements should increase battery life by 10% on newer Mac models.
To be able to download the Mavericks code named OS from the Mac App Store you'll need at least Snow Leopard 10.6.7. The new OS runs on all systems that are compatible with Mountain Lion.