The term in the modding community usually refers to an IPA that has been tested for stability, is free from malicious code, and works with current sideloading tools. Because Apple does not allow modified apps on the official App Store, you must source these from reputable third-party repositories. Popular sources for verified IPAs include:

Modded IPAs typically offer a suite of "cheats" that are pre-baked into the application: Currency Unlocks: