APK, Android Package File (.apk)
The APK Archive file format
APK (short for Android package) is the package file format used when installing and distributing application software and middleware on Android systems by Google. Blackberry 10 devices (OS version 10.2.1) can also use these types of files. Android phones are based on the Open Handset Alliance with a platform based in Linux. Google uses Android’s Software Development Kit (Java-based) to create APK file standards. Files within the archive are installed automatically.
Technical details of APK files
APK files resemble software packages for MSI. Once all pieces for the APK file are compiled, they are put into one file along with the coding for the program (including DEX files), resources, assets, certificates, and manifest files. APK files are archived using a zipping function, based on the JAR file format. One directory within an APK file may be a META-INF directory containing the following: MANIFEST.MF, CERT.RSA, CERT. SF. These are the manifest and certification files. Other directories commonly found in APK files include: LIB, RES, ASSETS, AndroidManifest.xml, classes.dex, and resourses.arsc files.