Impeachment begins in the House, the lower chamber, which debates and votes on whether to bring charges against the president via approval of an impeachment resolution, or “articles of impeachment,” by a simple majority of the House’s 435 members.
If the House approves such a resolution, a trial is then held in the Senate. House members act as the prosecutors; the senators as jurors; the chief justice of the U.S. Supreme Court presides. A two-thirds majority vote is required in the 100-member Senate to convict and remove a president. This has never happened.