I've noticed that some released games have been re-made with different translations or some were hacked and seem to be entirely different games. Castelvania and Zelda seem to have a half million different versions. Anyone know about these?
There are translaions, hacks and homebrew.
Translations are basically the same game as the original, just in english. Some minor changes might be made.
Hacks are modifications to existing games. The Castlevania and Zelda games are hacks - someone basically creates a new game based on the existing data. Modifying levels, enemies, story, etc.
Homebrews are new or unique games based on a game engine from another title, or just built from the ground up. Somebody making an NES version of The Hunger Games would be a homebrew.