What does the contents of an APK file include and what files are stored in it?

APK (Android Package) is an archive file containing all the necessary components to install an Android application. Inside an APK, you typically find:

• AndroidManifest.xml — the manifest file describing the app, its components, and permissions.
• classes.dex — the compiled bytecode of the app for the Dalvik/ART virtual machine.
• resources.arsc — the compiled app resources (strings, styles, etc.).
• res/ — a folder with uncompiled resources (images, layouts, sounds).
• lib/ — native libraries for different processor architectures.
• META-INF/ — metadata and signatures for APK integrity verification.

Essentially, an APK is a zip archive that can be unpacked and its contents examined.