A Video Game tune, sometimes the Background Music, is turned into a huge orchestral version by the game developers. (Or, in some cases, another band.) It is almost-never used within the game or series and is only available online or in stores. This is usually done because the game itself has limitations on the quality of the music if it is an 8-bit, 16-bit, etc. game. The music is not always the same thing, and is sometimes extended. It may also be worse than the original music depending on who you talk to. Not always limited to video game music, but is rarely seen in other media.