Black holes are regions in space where gravity is so strong that nothing, not even light, can escape. They form when massive stars collapse under their own gravity after exhausting their nuclear fuel. According to **Einstein’s theory of general relativity**, black holes warp spacetime, creating a point of infinite density called a **singularity**. The boundary around a black hole, known as the **event horizon**, marks the point beyond which nothing can return. Inside, spacetime curves infinitely. Black holes play a crucial role in understanding gravity, quantum mechanics, and the behavior of matter under extreme conditions in the universe.