A black hole is a region of spacetime with extremely strong gravitational forces, from which nothing—not even light—can escape. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of this region is called the event horizon. Anything, including light, that passes through the event horizon is trapped within the black hole and cannot escape.

Black holes are formed by the gravitational collapse of massive stars or other objects. When a star dies, it can collapse under its own gravity, creating a black hole if it is sufficiently massive. The remnants of the star, such as its electrons, protons, and neutrons, are squeezed into a tiny space, forming a singularity. The gravitational field around the singularity is so strong that nothing can escape.

Black holes are classified into several types based on their properties, such as their mass, charge, and rotation. Stellar black holes are formed from the collapse of massive stars. Supermassive black holes, which are much more massive than stellar black holes, are found at the centers of most galaxies. Primordial black holes are theorized to have been formed in the early universe.

The study of black holes has been a major area of research in theoretical physics and astrophysics. Black holes provide a unique opportunity to test the predictions of general relativity and to understand the nature of gravity. They have also been the subject of much speculation and popular culture, often depicted as mysterious and dangerous objects.