A charged black hole, also known as a charged or electrically charged Reissner-Nordström black hole, is a theoretical type of black hole that possesses an electric charge. In the context of Einstein's theory of general relativity, a black hole is formed when a massive star undergoes gravitational collapse, concentrating its mass into an infinitely dense singularity surrounded by an event horizon from which nothing, not even light, can escape.
When considering the possibility of a black hole having an electric charge, one must extend the mathematics of the Schwarzschild black hole solution to account for the electromagnetic field. The charged black hole solution is known as the Reissner-Nordström metric. In this solution, the black hole's mass and electric charge determine its properties, including the location of the event horizon and the curvature of spacetime around it.
It's important to note that charged black holes are currently theoretical constructs and have not been directly observed in the universe. While astrophysical black holes are generally believed to be formed from the gravitational collapse of massive stars, factors such as the distribution of charges and the astrophysical conditions make it unlikely for a significant net charge to develop in a black hole. As of my last knowledge update in September 2021, no definitive evidence of charged black holes has been found.