compileSdkVersion:
The compileSdkVersion is the version of API the application is compiled against. You can use Android API features involved in that version of the API (as well as all previous versions).
For example, if you try and use API 15 features but set compileSdkVersion to 14, you will get a compilation error. If you set compileSdkVersion to 15 you can still run the app on an API 14 device as long as your app’s execution paths do not attempt to invoke any APIs specific to API 15.
targetSdkVersion:
The targetSdkVersion indicates that you have tested your app on (presumably up to and including) the version you specify. This is like a certification or sign-off you are giving the Android OS as a hint to how it should handle your application in terms of OS features.
For example, setting the targetSdkVersion value to “11” or higher permits the system to apply a new default theme (Holo) to the application when running on Android 3.0 or higher. It also disables screen compatibility mode when running on larger screens (because support for API level 11 implicitly supports larger screens).
