Key items:
U.S. Congress Members: 535 (total)
U.S. Senate: 100
U.S. House of Representatives: 435 (two from each state)
Census: count of every living person in the U.S. every ten years. Among other items, results determine number of seats each state will have in the U.S. House of Representatives, they are also used to draw congressional and state legislative districts.
Apportionment: the determination of the proportional number of members each US state sends to the House of Representatives, based on population figures.
Redistricting: divide or organize (an area) into new political or school districts
Gerrymander: manipulate the boundaries of (an electoral constituency) so as to favor one party or class.
Gridlock: political stalemate refers to a situation when there is difficulty passing laws that satisfy the needs of the people.
Helpful resource and maps to better understand these actions: WA State Redistricting Maps