Android apps are getting bigger and bigger so with this increase in the app size, Google increased the size of apps from allowed 50MB to a whooping 4-Gigabyte to be hosted in the Android Market. Android apps like high-quality 3D interactive game with more than 50MB in size are hosted outside the Android Market and developers has this burden due to extra cost of server hosting. Only the Android application package (APK) is stored inside the market and if you download the app you will download the extra resources from 3rd-party server though it is done automatically.
Who will benefit with this new move from Google? Android Game developers will be the biggest beneficiary because most of the apps that is 50MB-plus in size are Android Games. The APK file is still at the maximum of 50MB and the main file is split into two expansion files. On newer devices when downloading an app from Android market this expansion files are downloaded automatically and refund will start right after the expansion has been download. For older devices the expansion files will be downloaded via the download library.