No doubt you've seen the stat showing how much more popular Android smartphones are than iPhones in much of the world. But many of those Android smartphones aren't the Android you're thinking of -- the kind you'd get from Samsung, HTC, or Motorola. That's because there's more than one Android. In fact, some analysts believe that about half of the Android devices in the world aren't ones you'd consider to be Android.
The other Android is called Android Open Source Platform (AOSP), and it's the truly open source part of Android, used as the basis of smartphones and tablets throughout the world.
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You can also think of AOSP as akin to DOS: the embedded core OS in Windows before Windows NT came along. In that thinking, the Windows GUI is analogous to Google Mobile Services (GMS), the set of services that runs on top of AOSP to deliver the complete Android experience. GMS is as proprietary as iOS or Windows Phone. Google doesn't charge money for it, but it comes with a lot of requirements that give Google a lot of control over Android devices. It's also part of all those Google services, from the Google Play app store to the Google Maps APIs that many Android devices rely on to provide their Androidness.
If you live in North America, Europe, Japan, Australia, or South Korea and other rich Asian nations, chances are you're using Android devices based on both the AOSP core and the GMS services that together represent the Google Android experience. Sure, manufacturers can add their own services and APIs on top of these two, but once you scratch those skins' surface, you're back to the Android experience.
In the rest of the world, chances are greater that your Android device is running AOSP. Thus, it doesn't provide much of the Google experience.
AOSP is used by most of the really cheap Android devices, such as those in China and India, as well as large parts of the rest of Asia, Africa, and Latin America. AOSP is cheaper to use because its services are so basic that it can run on inexpensive hardware better suited for the small incomes of poor countries. It also ironically is a good fit in countries like China where the government doesn't want a foreign company to have that much reach into citizens' data and communications -- where the government wants to keep that pile of riches for itself.
AOSP is also what Amazon.com's Kindle Fire tablet OS is based on and why it offers none of the Google services you'd expect from Android. Amazon has to replicate any of the GMS services such as an app store that it wants to offer -- and Amazon is one of the few companies that can do that.
In China, Xiaomi is in a similar position to make such technology investments, and that's why it hired a key Google exec, Hugo Barra, last year. If Microsoft's soon-to-be-subsidiary Nokia announces an Android device next week as rumored, it may also be an AOSP-based device, not a "real" Android device -- Microsoft also has the resources to replicate key GMS features using alternative technologies. (Why it would do so is another question!)