Android is linked to many phones, Google offers nice programs (Google Play, Translator etc) which gets built in there and lets you use it universally.
But I usually consider android as a 'cheap hand' since it can still catch a virus, or be ran on your PC, plus some devices doesn't have a multitouch function in their base.
Unlike the iPhone, mostly known as the first touch phone, has its own OS, own GUI (Apple was the first to invent GUI's btw), on some relative stuff.
IMO, most phones in the market are usually a small copy of an iPhone, like Google made something similar to Siri, Android Tablet are originally from an iPad (the idea and the system), Multitasking have been added to the iPhone before other devices, there was no android market before the Apple Store on iPhone 2G but they used to install apk's directly. I bet you guys 20$ that Android devices are going to have a Cloud app (iCloud).

Installous.

Not all android apps work with all androids. Only less than quarter.