Where They Go

When you run your app in Android Studio, it creates an APK to install on the device. That APK will wind up inside of the module’s build/ directory. build/ contains all sorts of outputs of the build process, the APK being chief among them:

Specifically, when you start off, you will find the APK in build/outputs/debug/app-debug.apk. By default, the filename will be based on your Gradle module name, so an app/ module winds up with an APK with app in the name. And, by default, you are creating a debug build — the sort of build that you as a developer will use — and so the APK winds up in a debug/ directory and has debug in the name.