A physical scan code is a device-specific identifier that is associated with each key, button or other control. Because physical scan codes often vary from one device to another, the firmware or device driver is responsible for mapping them to standard identifiers such as HID Usages or Linux key codes.
An Android key code is a standard identifier defined in the Android API for indicating a particular key such as 'HOME'. Android key codes are defined by the android.view.KeyEvent class as constants that begin with the prefix KEYCODE_.