Original: Investiture , from the Latin ( preposition in and verb vestire , ` dress ' from vestis ` robe ' ) is a rather general term for the formal installation of an incumbent ( heir , elect of nominee ) in public office , especially by taking possession of its insignia .
Simplified: The question who should invest ( appoint ) whom was the subject of a conflict between the Catholic church ( mainly the papacy ) and state ( mainly the Holy Roman Empire ) in the Middle Ages during the so-called lay investiture controversy .