If a federal official commits a crime or otherwise acts improperly, the House of Representatives may impeach—formally charge—that official. If the official subsequently is convicted in a Senate impeachment trial, he is removed from office.
Origins and Development
Constitutional Authority Article I, section 2, clause 5 Article I, section 3, clause 6 & 7
Impeachment: An Overview of Constitutional Provisions, Procedure, and Practice CRS Report (pdf)
Grounds for Impeachment
Process and Rules
Impeachment Trials in the Senate