Article I of the Constitution vests all legislative powers in Congress and lists its powers first, before those of the President or the courts. The framers made Congress bicameral so that the two chambers, chosen differently and serving different terms, would check each other. Today Congress is a large institution, with roughly 30,000 staff across member offices, committees, and support agencies.
This guide explains how Congress is organized, who leads it, how committees and floor procedures work, and how it uses its powers over money, nominations, and oversight.
Any member can introduce a bill, and thousands are introduced each Congress, but only a few percent become law. The House operates by majority rule under special rules for each bill, and a discharge petition signed by 218 members can force a vote the leadership opposes. The Senate runs largely on unanimous consent, and any senator can filibuster most legislation, which then requires 60 votes to end debate. Nominations and budget reconciliation bills need only a simple majority.
Each chamber divides its work among standing committees with jurisdiction over subjects such as taxes, defense, or agriculture, along with subcommittees. Committees hold hearings, mark up bills line by line, and decide which bills advance. Select committees handle special subjects, joint committees include members of both chambers, and conference committees, once common, resolve differences between House and Senate versions. In the House, the Rules Committee sets the terms of debate for most major bills, giving the majority leadership tight control.
Each Congress begins on January 3 of odd-numbered years and has two annual sessions, punctuated by recesses when members return home. Sessions after a November election are called lame-duck sessions. Members rely on personal and committee staff, and on nonpartisan agencies: the Congressional Budget Office scores bills, the Congressional Research Service provides analysis, the Government Accountability Office audits agencies, and the Library of Congress serves both Congress and the public.
The House elects a Speaker, in practice the majority party's choice, who controls the floor, refers bills to committees, and is second in line to the presidency. Majority and minority leaders and whips organize each party. In the Senate, the Vice President is the presiding officer but rarely attends, the President pro tempore holds a mostly ceremonial post, and the majority leader's right to be recognized first makes that office the Senate's real agenda-setter.
Congress's power of the purse runs through the appropriations committees, which write the twelve annual spending bills, and through tax-writing committees. The Senate's advice and consent shapes the executive branch and the courts. Oversight, through hearings, investigations, and subpoenas, lets Congress examine how laws are carried out, and contempt of Congress is its tool when witnesses refuse to cooperate.
Representatives must be at least 25 years old and citizens for seven years, and senators at least 30 and citizens for nine years. House seats are apportioned by population after each census, while every state has two senators regardless of size. The House initiates revenue bills and impeaches, and the Senate confirms nominees, approves treaties, and tries impeachments. Five delegates and a resident commissioner represent D.C. and the territories in the House without full voting rights.
Follow legislation step by step in how a bill becomes law, compare the chambers in the House vs. the Senate, or meet the leaders in congressional leadership: who's who.