The Android mobile operating system is used by millions of devices -- from smartphones to tablets -- all over the world. Developed by Google and based on Linux, Android allows users to create and share apps for a number of personal and business reasons.
APK -- Android Package File -- is a file extension for a software package that allows people to create Android apps. When you see the APK extension on a file, you know that the software package has all the required files and components that have been compressed into a single container file.
Since the Android operating system uses the basic Zip compression and decompression technology, you don't have to load any other type of software to access the APK compressed files. You can use the standard WinZip program or other file compression utility to open an APK file.