Why is Amazon different? Simple – it's perhaps the only third-party, legit app store owner, and developer interest in its platform is more than healthy enough. This results in devs often planning releases for Amazon's platform as well as Google's and Apple's. Of course, since the Amazon Appstore is a direct competitor to the Play Store, it is not allowed on the latter's pages. But that doesn't mean you can't get it on your device manually, and it's real easy!
But having the Play Store already loaded on your device, you might wonder what good installing Amazon's Appstore would do you. The answer is, again, simple – in order to keep users involved, Amazon has daily deals on apps, some of which include premium ones that would typically cost you a small fortune to get on the Play Store. When part of the daily deal batch, however, those usually see their price tags halved or pushed down to zero dollars, so long as you get them through Amazon's Appstore.
Here's how to install it: