Two principal tactics are used in gerrymandering: "cracking" (i.e. diluting the voting power of the opposing party's supporters across many districts) and "packing" (concentrating the opposing party's voting power in one district to reduce their voting power in other districts).[3] The third tactic, shown in the top-left diagram in the diagrams to the right, is that of homogenization of all districts.
The purpose is to help or hinder a particular demographic, such as a political, ethnic, racial, linguistic, religious, or class group, such as in U.S. federal voting district boundaries that produce a majority of constituents representative of African-American or other racial minorities, known as "majority-minority districts"
The problem is that it causes increased incumbent advantage and campaign costs , less descriptive representation , or using prisoners as voter count.