Exorcism
In Christianity, exorcism is the practice of casting out demons. In Christian practice the person performing the exorcism, known as an exorcist, is often a member of the Christian Church, or an individual thought to be graced with special powers or skills. The exorcist may use prayers and religious material, such as set formulas, gestures, symbols, icons, amulets, etc. The exorcist often invokes God, Jesus and/or several different angels and archangels to intervene with the exorcism. Protestant Christian exorcists most commonly believe the authority given to them by the Father, Son, and Holy Spirit (the Trinity) is the source of their ability to cast out demons.
Excommunication
In the Catholic Church, excommunication is normally resolved by a declaration of repentance, profession of the Creed (if the offense involved heresy) and an Act of Faith, or renewal of obedience (if that was a relevant part of the offending act, i.e., an act of schism) by the excommunicated person and the lifting of the censure (absolution) by a priest or bishop empowered to do this. "The absolution can be in the internal (private) forum only, or also in the external (public) forum, depending on whether scandal would be given if a person were privately absolved and yet publicly considered unrepentant." Since excommunication excludes from reception of the sacraments, absolution from excommunication is required before absolution can be given from the sin that led to the censure. In many cases, the whole process takes place on a single occasion in the privacy of the confessional. For some more serious wrongdoings, absolution from excommunication is reserved to a bishop, another ordinary, or even the Pope. These can delegate a priest to act on their behalf.