Android devices require all applications to be signed before installation. A signed mod APK allows you to install the game on a standard, non-rooted device just like a regular app.
Modified versions of idle RPGs like Loop Viking often promise to remove "the grind" by offering: Download Loop Viking Idle Hero Mod Signed apk
Increased XP gain or faster hero leveling. Android devices require all applications to be signed
In the context of modded games, a "signed" APK refers to a modified file that has been digitally re-signed with a new certificate. Download Loop Viking Idle Hero Mod Signed apk