Senators serve on four types of committees. Standing committees, the most important type, deal with bills concerning specific legislative subjects. The Senate has 17 standing committees, the most powerful of which include Appropriations, Armed Services, Foreign Relations, and Judiciary. Select committees, also called special committees, are temporary groups formed for investigations or other special purposes. Conference committees and joint committees consist of members of each house of Congress.
Conference committees resolve differences in bills that have passed in both houses.
Joint committees deal with topics that concern both houses, such as energy problems and economic matters. Most Senate committees are divided into subcommittees, which handle much of the committee work. Members of the majority party head most of the committees and subcommittees. Members of both parties vote for committee heads. Often, however, the seniority principle determines who serves as the head of a committee.