Gerrymandering is the name of the practice of drawing boundaries for electoral areas so as to give unfair advantage to a given political party.
Reapportionment of election districts must be done by state legislatures at least once every decade, after the census has been completed and the most recent figures of population location are available. The goals of the redrawing of district lines are to create districts that are as close as possible to having the same number of potential voters in each district and to keep the districts as compact as is feasible.
Gerrymandering comes into play if districts are created that group large numbers of voters from one political party in the same district in order to increase the likelihood of that party being able to control the outcome of elections in that area. Gerrymandering is also seen at times in efforts to divide interest groups such as a particular ethnic population into a number of electoral districts so as to reduce the impact of voters from that group. Courts have ruled that artifical divisions of areas are not constitutional, and are regularly asked to review newly proposed electoral districts that are perceived to be giving unequal representation to a group of voters as a result of gerrymandering.