To impeach means to charge a public official with misconduct in office, often in order to remove them from their position of power.
Charges are filed by a formal accusation or indictment presented to a governing body, such as a legislature or court, alleging that the official in question has committed a "high crime or misdemeanor" or other serious offense. The specific process for filing charges can vary depending on the governing body and the nature of the offense being alleged.
Guilt is determined through a legal process that varies by country and jurisdiction. In general, guilt is determined by a court of law based on the presentation of evidence and arguments from both the prosecution and defense. The prosecution must prove the defendant's guilt beyond a reasonable doubt, and the defendant is presumed innocent until proven guilty. The judge or jury then makes a decision based on the evidence presented and any applicable laws.