A black hole is a region in space where the gravitational pull is so strong that nothing, not even light, can escape from it. This phenomenon occurs when a massive star collapses under its own gravity at the end of its life cycle. The boundary surrounding a black hole is called the event horizon, beyond which no information can return. Black holes can vary in size, with stellar black holes forming from individual stars and supermassive black holes existing at the centers of galaxies, including our own Milky Way. Scientists study black holes to understand the fundamental laws of physics and the nature of the universe.