A Place Where Gravity Wins
A black hole is one of the most extreme objects in the universe. It is a region of space where matter has been packed so tightly that its gravitational pull becomes overwhelming. The defining feature of a black hole is that nothing can escape it once it gets too close — not even light, the fastest thing in the universe. This is why a black hole is "black": no light can leave it, so it cannot be seen directly. It is detected instead by its powerful effect on the space and matter around it.
The Point of No Return
Every black hole has a boundary called the event horizon. This is not a solid surface but an invisible line in space. Anything that crosses the event horizon can never come back out, because escaping would require travelling faster than light, which is impossible. Outside the event horizon, it is still possible to move away. Inside it, every possible path leads deeper toward the center. The event horizon is, quite literally, a point of no return.
How Black Holes Are Born
Many black holes form from the deaths of massive stars. When a star far larger than our Sun runs out of fuel, it can no longer support itself against its own gravity. The core collapses inward suddenly and violently, and the outer layers may be blown away in a brilliant explosion called a supernova. What remains is a collapsed core so dense that it becomes a black hole. There are also supermassive black holes, millions or billions of times the mass of the Sun, that sit at the centers of galaxies, including our own Milky Way.
Seeing the Invisible
Although a black hole itself emits no light, astronomers have clever ways of finding them. As gas and dust spiral toward a black hole, they heat up and glow brightly before crossing the event horizon, producing radiation that telescopes can detect. The motion of stars orbiting an unseen, massive object is another strong clue. In recent years, scientists even captured images showing the dark silhouette of a black hole surrounded by a glowing ring of superheated material — the closest humanity has come to "seeing" one.
Source
This article was written using information from Wikipedia.