The definition of an interest group is a collection of individuals who are united by a shared purpose or common interest in the promotion of a political agenda. Interest groups play a key role in American politics by advocating for the rights of their members, influencing public opinion, and attempting to shape public policy. Interest groups span the political spectrum, representing both liberal and conservative causes. Examples of interest groups include the National Rifle Association, Planned Parenthood, and the American Civil Liberties Union. These interest groups are distinct from political parties in that their memberships are voluntary and their goals are particular to their members' interests rather than a party's platform. While interest groups can be powerful forces in the political landscape, they can also be limited in scope, lacking the ability to influence national elections and federal legislation. Nevertheless, interest groups are essential to the American political system and the protection of individual rights.