The definition of spiritualism (or spiritism) is that the personality of the human can survive death and can communicate with the living through a medium.
It is believed that the spiritualist movement started with the Fox sisters in 1848 in upstate New York. The Fox sisters asserted that they could communicate with spirits by rapping on tables. (It was later learned that the rappings were actually made by cracking their toe joints.) Approximately 30 years later, the Fox sisters admitted their fraud, but by that time, there were tens of thousands of mediums holding séances. These mediums caused, or created, spirits to entertain the attendees by making sounds, making objects appear and/or move, making lights glow, and levitating tables.
These mediums revealed their psychic powers, including clairvoyance (an alleged psychic power to see things beyond the range of the vision); clairaudience (perception of messages in thought forms from an entity; a form of channeling); telekinesis (the ability to bend and move objects with the mind); and telepathy (direct transference of thought from one person to another without using the usual methods of communication).
It wasn’t until the 1920’s, when magicians such as Houdini exposed the methods of the deceptive practices used by mediums to fool the public, that the spiritualist movement slowed down.
Actually the version of séances seen in the movies are rather accurate. As you see in the movies, there are people sitting around a table in a dark room, holding hands with a medium who fakes a trance and relays to the group information given by the spirit. The session is often accompanied by tricks such as mysterious sounds, appearing objects and levitating tables.
Many people believe in spiritualism as scientific proof of the afterlife without having to believe in a certain religion.