If you mean "Leaf Green", it, a long with Fire Red, are remakes of the two original games in Japan, Pocket Monsters Red and Green (for us, Pokemon Red and Blue). FR and LG aren't just ports with updated graphics, though, as they contain a brand new location called the Sevii Islands which is inhabited by lots of Johto species'. The Elite Four also have a second version (aka. different Pokemon and much higher levels). All in all, pretty good set of games to own.
... But by the off chance this has nothing to do with what you were wondering, sorry about the rambling ^^;