Most black holes are created from star remnants after a supernova explosion. Smaller stars become thick neutron stars, which are not gigantic enough to trap light. If the star’s total mass is large enough, it can be proven theoretically that no force can keep the star from collapsing under the influence of gravity, but as the star collapses, its surface nears an imaginary surface called the "event horizon," where time on the star slows relatively to the time kept by observers far away. When the surface reaches the event horizon, time stands still. The star can no longer collapse. It is a frozen object.
Bigger black holes can result from stellar collisions. The basic formation process is known, but one mystery in the science of black holes is that they appear to exist on two radically different size scales. There are the countless black holes that are the remnants of massive stars. Peppered throughout the universe, these "stellar mass" black holes are generally ten to twenty-four times as massive as the Sun.
There are a lot of people who are confused about black holes and how dangerous they can actually be. When you try to place yourself inside a black hole, your body will fall at different times. It can be confusing. When a star dies, it may leave a black hole in the place of where it used to be.
The black hole can only become bigger if the leave is already huge, to begin with. The problem with big black holes is that they may continue growing. It can make itself grow bigger as it gets the star mass. This is a topic that is still constantly being monitored by those who are interested in the solar system.