(I'm back from my break!)
Possessions is when a demonic spirit takes control of the living. This happens more often than what most people thinks, but it is still rare. This doesn't happen right away, there are three stages of possession.
Infestation: This is the first stage. This is when a demon lives in a house, but never chosen a human to possess. Sometimes it lives there without disturbing the living and sometimes it doesn't want to possess anyone.
Oppression: This is the 2nd stage. This is when it has chosen a human to possess. It doesn't have full control, but is trying to do so.
Full Possession: This is the final stage. It is when the demon has full control of the human. The demon can bring death to it's living host.
When someone is 2nd or 3rd stage of possession anything that is religious or that has been blessed, like holy water or rosaries, it feels almost like fire to them. Sometimes food or water tastes horrible to them, because demons doesn't want the human to be strengthened and rejects all food and water. This could mean a sign of death during a possession. They try their best to not let the human know what is going on.
Sometimes it's human host isn't always in full possession. Instead they are fully possessed at random times, on and off. They either don't know at all what they did or it was foggy in their minds of what they did, when they were possessed, unless someone tells them.
Exorcism usually takes alot of time. For example, Carl Lawson's exorcism lasted for about six hours and I know another story about a exorcism done on a boy that lasted 8 hours.