These are modified versions of original Pokmon game files, designed to be played on Android devices through the use of emulators. These modifications often introduce alterations to the storyline, characters, gameplay mechanics, or even the graphical elements of the original games. An example would be a version of Pokmon FireRed with an entirely new region to explore and Pokmon not originally found in the Kanto region.
The appeal of these altered games lies in their ability to offer unique experiences beyond what the official titles provide. This can include increased difficulty, enhanced features, and novel narratives. Historically, the creation and distribution of these modifications have been a community-driven effort, with passionate fans developing and sharing their creations online. This is done in a legal gray area, since the original games are owned by Nintendo.