White holes are bizarre objects that are related to black holes.
White holes and black holes are both described mathematically by the theory of general relativity. Although theoretically possible, no white holes have been found in the Universe. While this gives you a rough idea of how white holes work, it isn't completely correct. Black holes are thought to be the dead remnants of stars, with gravitational fields so intense that within a certain radius of the hole, known as the event horizon, the escape velocity exceeds the speed of light. The physical effects near a white hole would be different.