What does fusion mean in Pokémon?

What does fusion mean in Pokémon? Fusion Strike System enables the player to draw cards until the number of cards they have in their hand is equal to the number of their Fusion Strike Pokémon in play. This Ability can be used once per turn for each Genesect V in play, which makes it possible to draw nearly half the deck in a single turn!

Fusion Strike System enables the player to draw cards until the number of cards they have in their hand is equal to the number of their Fusion Strike Pokémon in play. This Ability can be used once per turn for each Genesect V in play, which makes it possible to draw nearly half the deck in a single turn!