Black holes are regions of space where gravity is so strong that not even light can escape. They come in different sizes, with stellar-mass black holes being a few times more massive than our Sun, and supermassive black holes found at the centers of galaxies. Supermassive black holes can have millions or even billions of times the mass of the Sun.
Another type of black hole, intermediate-mass black holes, falls between stellar-mass and supermassive black holes. These mysterious objects are still not well understood, and scientists are actively studying them. Understanding black holes is crucial to our knowledge of space-time and gravity.