The size limit regarding applications on the Android Market has been 50MB for quite some time now; this file weight was usually enough for most applications but with high-quality, demanding games being more and more visible, the upper limit had to be changed.

Google has done just that and went from the previous 50MB to (a close to insane) 4GB. Before you raise your eyebrows too much, APK files will still remain limited to the good old 50MB but they’ll be able to have expansion files attached. The limit for expansion files is 2GB and each app can have two expansion files up to that size, regardless of the file format. Additionally, Google also throws in file hosting so you have one less thing to worry about.

Source: Android Developers