Impeachment is the formal charge by the house of representatives that a government official has committed "Treason, Bribery, or other high crimes and Misdemeanors."
Though many of us have heard and know of impeachment, it doesn't happen to often in the United States. The legislative will have to make high level chargers against the government to possibly get an impeachment approved. Although it doesn't always mean removed from office, most are getting criminal actions taken on them.