Black holes represent some of the universe's most extreme and enigmatic phenomena, regions where gravity is so immensely powerful that nothing, not even light,...
A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation like light—can escape from it. The boundary beyond which escape is impossible is called the event horizon.
Stellar black holes form from the gravitational collapse of massive stars at the end of their life cycle. Supermassive black holes, found at the centers of most galaxies, are thought to grow by accreting vast amounts of matter and merging with other black holes.
Black holes themselves are invisible because they do not emit light. However, their presence is detected indirectly by observing their powerful gravitational effects on surrounding matter, such as the swirling accretion disks of gas and dust that heat up and emit X-rays, or gravitational lensing of background objects.
Approaching a stellar black hole, you would experience extreme tidal forces, 'spaghettifying' your body. Once past the event horizon, escape is impossible, and you would be inevitably pulled towards the singularity at the center, though the exact experience beyond the horizon is a matter of theoretical physics.