Force ghost

The Force ghost was the soul and essence of a deceased Force-sensitive who denied the will of the Force upon death, yet was able to interact with the living. It also described those who had come to terms with death and invoked this technique to preserve their identity, manipulating their own pneuma to guard against being absorbed into the Force in such a way that they would lose their identity. Some Sith Lords learned similar techniques, which in some cases were combined with the art of Essence transfer, and thus allowed them to physically interact with their environment. This ability also allowed the Force user to interact with both living beings and other Force ghosts.

Text and facts from the “Force ghost/Legends” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.