The U.S. Constitution vests the power to impeach in the House of Representatives, while charging the Senate with the power to try impeachments. The House votes whether to bring the charge, and the Senate tries the case. The House vote is by simple majority, but the Senate requires a two-thirds majority to convict.
The grounds for impeachment are: “Treason, Bribery, or other high Crimes and Misdemeanors.”
To initiate the impeachment proceedings, a document or “resolution calling for a committee investigation of charges against the officer in question” must be referred to the House Committee on Rules, which may refer it to the Judiciary Committee for investigation. The Judiciary Committee may vote to try the case, and the Senate will proceed with a trial and a vote. In an alternate procedure, the resolution can directly call for impeachment, in which the resolution goes directly to the Judiciary Committee for review.