A standing committee is a group of members of a larger body, such as a legislature or membership association, appointed for a specific purpose and, usually, a specific period of time. In the United States Congress, both the House and Senate establish many standing committees, each with its own specific jurisdiction. For example, the Senate Committee on the Judiciary is a standing committee that reviews all proposed legislation regarding judicial matters. The committee typically either reports its findings to the full Senate for that body's action, or simply tables it &emdash; that is, the group issues no report at all, essentially killing it.
The standing committees of the houses of congress are established not by the U.S. Constitution, but by the rules that each house sets forth by Constitutional mandate. The House of Representatives' Rule X calls for 20 standing committees, and the Senate's Rule XXV establishes 16 standing committees. A standing committee itself may have subcommittees to deal with more specific issues; for example, the Senate Committee on Health, Education, Labor and Pensions has three subcommittees, one on Children and Families, another on Employment and Workplace Safety, and a third on Retirement and Aging. Most committees in each House have subcommittees.
Members are appointed to the standing committees and their subcommittees by the leadership of the party in power in each house. When possible, members' preferences are taken into account when committee assignments are made, but these assignments are often used to reward or punish members as well. There will usually be more members of the majority party on each standing committee than of the minority party, and committee chairs are elected by simple majority, resulting in committees in each House nearly always being chaired by a member of the majority party.
The standing committees are a critical component of the Congress, without which it could not effectively operate. With so many issues daily coming before the Congress, it's impractical for the full House or the full Senate to try to address each and every one of them in the kind of detail necessary. By delegating all issues to the appropriate standing committee or subcommittee, the congress establishes an orderly work flow and division of work, and restricts the issues it deals with to those assigned that priority by the committees themselves.
The standing committees and their chairs tend to be powerful in the legislature of the U.S., as do committees and their chairs in most U.S. state legislatures and in legislatures worldwide. Proposed legislation cannot ordinarily be considered by the full body, for example, without the approval of the committee with jurisdiction over its subject matter, and the committee cannot consider it unless the chair places it on the agenda. In addition, people nominated by the president to fill important jobs in the government cannot assume office until they've been confirmed by the Senate, a process that can take place only after the appropriate standing committee has considered the nomination and passed it on to the Senate.