.apk stands for Android Package Kit extension & developed by Google under the OHA (Open Handset Alliance). It is used for distributing and installing collection of component on the Android Operating System. It also contain all the files that related to a single android application & this file itself compressed into a collection of files like AndroidManifest.xml file, resource file, application code(.dex file) and other files. Our android project are compiled into a single .apk file.

The .apk file extension contains the collection of .dex (Dalvik Executable) file that behave as a single project or application file for use with the android platform. It is simple just ZIP archive, but APK files have pre-defined specific structure.