The three types of gerrymandering are excess vote, wasted vote and stacked. The excess vote method concentrates the voting power of the opposite party into very few districts, meaning the party's overall influence is reduced.
The wasted vote method spreads the power of the opposing party across many districts so it is unable to obtain a majority vote. The stacked method involves drawing oddly shaped boundaries to place the power of the majority party into areas far removed from one another but in the same congressional district. Redrawing may be done once every 10 years after the nationwide census is taken.