A stellar black hole represents a region of spacetime exhibiting gravitational pull so strong that nothing, not even electromagnetic radiation, can escape its confinement. These objects form from the catastrophic gravitational collapse of extremely massive stars at the end of their life cycle. The defining feature is the event horizon, which marks the boundary point of no return; anything crossing this threshold is inexorably drawn toward the object's singularity at the core. The presence of a black hole is primarily detected by observing the effects of its intense gravitational field on nearby stars and gas, such as the spiraling accretion disks of matter that emit detectable X-rays as they fall toward the boundary.