The House needs only a majority of votes in order to impeach the President of the United States. Impeachment is only the first step and is the equivalent of an indictment. If the vote passes the House, it is followed by a trial in the Senate.
The articles of impeachment are sent to the Senate, where the actual trial is held. Once both sides present their case, the Senate votes on whether to convict or not. A two-thirds vote is required to convict. Impeachable offenses are treason, bribery or other high crimes or misdemeanors. High crimes and misdemeanors involve breaking a law, abuse of power and violating the public trust. Only two presidents were impeached, Andrew Johnson and Bill Clinton, and both were acquitted.