OS X Snow Leopard is an operating system that many Mac users know and love, and while it was a well-built and refined release, there have been five new OS X releases since its release.
Some people have stayed with OS X Snow Leopard because they own Mac computers that aren't compatible with later operating systems. Other are sticking with it for personal reasons. In any case, Apple has released a small update to Snow Leopard that ensures "future compatibility with the Mac App Store."
It's important to note that doesn't mean that Apple is going to continue to support OS X Snow Leopard, but rather that Apple will be able to continue to offer more modern operating systems to Mac users who have compatible computers. These users will be able to directly update from Snow Leopard to any new operating systems, including the latest release, El Capitan.
Those who can upgrade to a newer operating system should really do so. There are plenty of advantages to newer OS X operating systems, and they're not just ease-of-use. Newer operating systems also tend to be more secure and are able to handle newer apps and software.
