The Senate conducts various types of business. Its main role is as the upper house in a bicameral legislature. However, it has other important duties, including presiding over impeachment trials referred by the House of Representatives and confirming certain presidential appointments, such as those of Supreme Court justices and appeals to district court judges. Once such nominees have been questioned and witnesses have been heard (a procedure similar to the committee stage in legislation), there is a debate on the appointment, followed by a vote.
Any Senator may introduce a bill to the Senate. After it is introduced, the bill is sent to the appropriate committee or subcommittee for review. If it is sent to a subcommittee and passes, it must then pass the full committee stage. The committee will hear testimony from experts, proponents, and opponents of the bill and has the power to subpoena these witnesses if they are unwilling to appear.
If the committee approves the bill, the majority leader tables it on the calendar. This is a crucial point in the bill's progress, as legislation placed low down on the calendar is unlikely to reach the debate stage at all. Debates in the Senate are relatively unstructured, as there are fewer formal procedures than in the House. During the debate, Senators may speak on any subject they choose, which means the bill may be defeated by filibuster. A majority of sixty senators can break a filibuster and force a vote on the bill by a process known as cloture. If the bill is passed, it is either sent to the House if it originated in the Senate or to the President for consideration if it has already passed the House.