The Mac App Store isn't just for downloads, it's where you do to make sure all those downloads are always up to date!
The Mac App Store is more than just a convenient way to download apps from companies that make Mac software. It's also the only way to download the latest system software updates. Not just major operating system updates like OS X Yosemite either, but also important security updates, incremental changes to support software, and all the apps you use every day.
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