Reapportionment is the allocation of seats in the House of Representatives to each state after each census. Redistricting is the redrawing of the boundaries of the congressional districts within each state. Most congressional districts are drawn along natural boundaries. As a result, most districts can be classified as coastal, suburban, inner-city or rural.
Gerrymandering is the redrawing of congressional districts to disadvantage another group or party. Gerrymandering has been used to disenfranchise blacks. If there are 600 white people, 650 white people and 5 congressional districts: fairly, there would be 3 black and 2 white representatives; unfairly, racial gerrymandering would occur. Also, gerrymandering has been used to disenfranchise anti-federalists as seen in Gilbert Stuart's illustration.