There are three types of black holes. They are stellar-mass, intermediate-mass, and supermassive. They all form different ways, and have very different masses. When a black hole is rotating, it is classified as a Kerr black hole. If it isn't rotating, we call it a Schwarzschild black hole.
Stellar-Mass Black Holes
Stellar-mass Black Hole with Partner Star
Stellar-mass black holes have masses of about ten Suns. They are created when massive stars reach the end of their long lives and run out of fuel, exploding in extremely powerful blasts called supernovas. The left-over matter collapses into itself, forming a stellar-mass black hole.
Intermediate-mass Black Holes
Intermediate-mass Black Hole pulling Matter from a Blue Star
Intermediate-mass black holes have masses that range from 100 Suns to 1000000 (1 million) Suns. Scientists are yet to figure out how they form, but they think they could be the central black holes of dwarf galaxies.
Supermassive Black Holes
Supermassive Black Hole emitting a Blazar
Supermassive black holes have masses ranging from 1000000 (1 million) Suns to 1000000000 (1 billion) Suns. These massive black holes are said to reside at the center of most, if not all, regular sized galaxies. Scientists believe that they form by the merging of smaller black holes, and they can grow over time as they pull matter into themselves.