How does a black hole form in space?

A black hole forms when a massive star, typically more than 20 times the mass of our Sun, reaches the end of its life. When the star exhausts its nuclear fuel, the outward pressure that counteracts gravity disappears, causing the core to collapse under its own enormous weight. This triggers a supernova explosion, and if the remaining core is massive enough, gravity overwhelms all other forces and crushes the matter into an infinitely dense point called a singularity, surrounded by an event horizon from which nothing, including light, can escape. Black holes can also form through other means, such as the collision and merger of neutron stars, or in the early universe through the direct collapse of massive gas clouds before stars even formed.