An Android application APK (short for Android Package Kit) is a file format used to distribute and install Android applications on mobile devices. The APK file contains all of the necessary code, resources, and assets for an app to run on an Android device. It also includes information about the app’s permissions and other configurations. Once you have downloaded the APK file, you can install it on your Android device by enabling the “Unknown Sources” option in the device’s security settings and then opening the APK file.