The president, vice president, civil officers of the United States, and federal judges can be impeached by the House of Representatives. Once a majority of the House votes to impeach, the case moves to the Senate where a two-thirds vote is necessary for conviction. Both Andrew Johnson and Bill Clinton were impeached by the House. Neither man was convicted by the Senate.
Article II, Section 4 of the Constitution sets the standard for impeachment as treason, bribery, or other high crimes and misdemeanors. Since high crimes and misdemeanors are not defined, the House has a lot of discretion when deciding on impeachment. This means that a person doesn’t need to be guilty of a criminal offense to be impeached.
Once impeachment occurs, members of the House called managers act as prosecutors and try the case to the Senate. When the president is on trial, the chief justice serves as the judge. The Senate is not only the jury. It also sets the rules for the trial. Issues like the amount of time each side has to present its case, the number of witnesses that can be called, and the length of depositions are set by the Senate. The federal rules of evidence do not apply.
Once the trial concludes, the Senate votes on the article(s) of impeachment. If two thirds or 67 senators vote to convict, the person is removed from office. Removal from office doesn’t result in a criminal conviction. Nor does it protect someone who has been removed from office from facing criminal charges based on the actions that led to removal from office.