A black hole is a region in space where the gravitational pull is so strong that nothing, not even light, can escape from it. It is formed when a massive star collapses in on itself.
Black holes can range in size from a few miles in diameter to billions of times the mass of our sun. The largest black holes, known as supermassive black holes, are thought to exist at the centers of most galaxies.
No, a black hole would have to be extremely close to Earth to cause any harm. The nearest known black hole to Earth is about 1,600 light years away, which is a safe distance. Additionally, even if a black hole did come near Earth, our planet's gravity would be strong enough to keep us in orbit.
Entering a black hole would result in a process known as spaghettification, where the intense gravitational pull would stretch your body into long, thin strands. As you get closer to the singularity (the point of infinite density at the center of a black hole), the gravity would become so strong that it tears apart the bonds holding your atoms together.
Nothing can escape a black hole once it has passed the event horizon, which is the point of no return. However, some things, such as Hawking radiation, can escape a black hole before reaching the event horizon.