A séance is the term that describes a communication between a group of two or several persons in the physical realm with one or more entities in other dimensions. It is also called Mediumship. A Medium is the person who contacts 'the other side.'
The word Séance comes from French séance, 'seat', 'session', from Old French seoir, 'to sit.' In French as in English the word came to be used specifically for a meeting of people to receive spiritualistic messages (a sense first recorded in English in 1845), but earlier in French and English the word had been used for meetings more generally.