The term Exorcism can be found in, among other religions, the Catholic faith, where a person's mind is possessed by an evil entity. Shamanism works with a common daemon concept.
The Protestant faith does not have daemons or devils in the same way. Everything - good as evil - is God's work.

If a person is possessed by a daemon or evil spirit, he can't act freely, acts evil, irrationally and to the danger of others.
Apparently, the exorcism depends on the victim's religious affiliation.

The modern world could call this person "psychotic". However, there are reports of possessions that cannot be explained so easily.
In the United States, a well-documented and famous exorcism was carried out in 1949. The victim was a young boy. This event led to the movie "The Exorcist", well-seasoned with exaggerations and special effects.
Possessions are commonplace in Hollywood movies. There are apparently two types of possessions:

Spiritual
possession
  • The possession may apply to a person, an animal or even an object.
  • The possession can be friendly or malicious.
  • The possessed, can speak in an unknown language, or "nonsense".
  • The person changes his voice unnaturally.
  • The person acts irrationally.
  • The person is aware of events that are otherwise impossible to know. Eg. future visions.
  • The spiritual possession can be based on both natural or supernatural entities. Eg. by a Muse who brings the ability to write poetry!

Daemonic possession
  • The possession is always about a person.
  • In addition to the characteristics of  the "spiritual possession", the person may be disfigured, have discharge from the mouth and nose, as well as being able to vomit  blood, metal, glass or other foreign matter.
  • The person shows intent or ability to harm others.
  • The possession is always on the basis of a malicious being.
  • The possession is always demonic and not human (alien, spirit).

The actual exorcism
In the Catholic faith, the Pope has blessed a few priests who can make an exorcism. If a house is possessed, this must first be blessed, as a cleansing or exorcism only can take place at a blessed area. If a person is possessed, he must first be moved to holy ground (Church or in a violent case a special room in the Vatican).
In other religions, there is also a specially trained person who can make an exorcism. Today, it is widely used to call clairvoyants and alternative therapists for help.

Everyone can exorcise and cleanse, according to critics!
And the criticism even comes from a Danish bishop from the 16th century! He believed that the church earned too much on poor people, and he made a very thorough manual that everyone can work with. Just  they are "Believers", as he writes. The text is called:  "Biskoppelig vejledning og ritual for dæmonbesatte:  Udarbejdet af Dr. Peder Palladius,1547".

Not completely harmless
It is not completely harmless to make an exorcism on your own. In many films and broadcasts, we see people who read the Bible or distribute incense. Others carry out a hand blessing to cure the possessed. If, however, it turns out that one has misinterpreted a mental illness (some possessions are apparently "just" a mental illness), you expose the sick to perhaps irreparable damage. It is reported - but unconfirmed - that the possessed can cause great damage to themselves and others.