Congressional reapportionment is the shifting of representative seats in Congress and occurs every 10 years after the national census. States may lose or gain in their population, so their number of representatives change. There is always 435 representatives in the House, so the representative spots just shift states. Congressional redistricting happens after reapportionment. Redistricting is the changing of district lines within a state. This may occur to to the addition or loss of representative(s). Each district has to have equal population, must be connected, and must be compact. Politicians may gerrymander to keep an incumbent in power. They change district lines to ensure that the majority of voters in the district will support the incumbent.
