A black hole is a region in spacetime in which the force of gravity prevents anything from escaping. It is made from a singularity that has the power to suck anything from it's intense gravitational pull, including light itself.
Anything in the known universe has the potential to become a black hole, once that object has crushed (compressed) into itself small enough that its density is so strong, ergo, you'll have a singularity (black hole).
So far on record, the only object that has the power to do that to itself is a star, a dying one.
Once a star has run out of fuel to power itself it won't just extinguish itself, instead it will implode into itself and create a supernover or hypernover (depending on the size of the star) and burst radiation through it's galaxy, you will then have a black hole.
The ring that black holes create is the light bending both in front and behind the black hole itself. The object that is behind the black hole is safe from the harm of its suction but light near the black hole is twisted and bend.
If you were hovering next to a black hole at the photon sphere (with no suction or any danger) you would literally see the back of your head just by the light being bent around the black hole.
Spaghettification (The noodle effect)Edit
If an astronaut were to fall into a black hole towards the event horizon (the point of no return) their body would be stretch atom by atom into the singularity. The victim would be dead before the violent process occurred.