A seance is an attempt to communicate with spirits (the dead). The seance, or sitting, is led by a person known as a medium, who will usually go into a trance that theoretically allows the spirits to communicate through her/him.
A seance is usually conducted in the dark, and the participants may join hands in a circle. The medium may use a number of methods to attempt communication, such as channeling through a trance, automatic writing, writing with a planchette (a pointer, can be used on a ouija board, to point to letters and numbers. Can also be used with a pen in it, to enable the spirit to write or draw) or they can use thoughtography.