Impeachment is the process by which a legislative body can level charges against a government official, such as a president. Article I, Section 2 of the United States Constitution vests the U.S. House of Representatives with the sole power of impeachment, and Article I, Section 3 vests the U.S. Senate with the sole power to try all impeachments. Should an impeachment inquiry be held, and the House of Representatives vote to impeach an official, the matter is then passed on to the U.S. Senate where a trial is held, presided over by the Chief Justice of the Supreme Court. For a conviction to take place in an impeachment proceeding, a supermajority (two thirds of the members present) must concur, and if they do, the official shall be removed from their office. While the Constitution prohibits a judgment in an impeachment trial from extending beyond removal, once an officer is removed he or she shall be liable and subject to indictment, trial, judgement and punishment.
Since taking office, President Trump has allegedly committed a number of unethical and illegal acts, some of which are impeachable offenses. Normally, if a person was to commit such offenses, they would be indicted and the matter would be adjudicated in a court of law. However, internal Department of Justice policy states that a sitting President cannot be indicted. Consequently, when a President is alleged to have commit a crime serious enough to be considered an impeachable offense, the U.S. Constitution provides a remedy in the form of impeachment.