A GenerationLocke is a Nuzlocke challenge where you play through one game of each region, in an order of your choosing. At the end of each game, you breed your surviving champion team and trade the eggs to the next game. When making the jump between generations, the team will need to be transported up to a completed (usually) version of a game from that generation, and then breed eggs. Or, if this is impossible for any number of reasons, using cheats to get roughly equivalent Pokemon in the next game is also allowed (easiest way here being changing a wild Pokemon encounter to be the Pokemon you need)
And the link in my comment might help, too.