A black hole is defined as a region of spacetime from which gravity prevents anything, including light, from escaping. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole.
A stellar black hole is a black hole formed by the gravitational collapse of a massive star. They have masses ranging from about 3 to several tens of solar masses. The process is observed as a hypernova explosion or as a gamma ray burst.
A supermassive black hole is the largest type of black hole, on the order of hundreds of thousands to billions of solar masses. Most—and possibly all—galaxies are inferred to contain a supermassive black hole at their centers.
Micro black holes, also called quantum mechanical black holes or mini black holes, are hypothetical tiny black holes, for whichquantum mechanical effects play an important role. It is possible that such quantum primordial black holes were created in the high-density environment of the early Universe (or big bang), or possibly through subsequent phase transitions. They might be observed by astrophysicists in the near future, through the particles they are expected to emit by Hawking radiation.