Supernovas are the phenomenon that mark the end of a star's life cycle. They occur when the internal gravity in a star is no longer high enough to continue the natural cycle of a star and it begins to release its internally stored energy. The result is a massive release of energy in the form of an explosion. The energy release is the resulting energy from the fusion of hydrogen atoms into helium atoms within the core of a star. The resulting explosion is extremely violent and bright, potentially releasing as much light from the explosion as the star did during its entire lifetime as a star, but in the span of a much shorter time period.
During a supernova, a star expels a tremendous amount of internal matter. This matter can take the form of heavy metals, such as iron. The explosion spreads this matter into space, continually moving until the matter meets with resistance, such as a planet, moon or other gravitational force. This matter moves at a speed between 9,000 miles per second and 25,000 miles per second. Remnants of this material exist throughout the galaxy, even forming some of the basic components in your body.
The spread of matter and force of the explosion performs two specific tasks in the universe that create a vital phenomenon. The spread of matter adds vital minerals to gaseous clouds in the universe, which are compressed by the force of the supernova explosion. When these clouds gain enough matter to begin forming gravity and are compressed enough to centralize that gravity, new stars can begin to form.
After supernovas where the star's large core remains intact, its gravity can begin pulling its own matter back toward the core. If the core's energy is expended, it becomes a point of high gravitation but no fusion potential. The result is a large center of gravity that can pull material from its own cloud, as well as from other bodies in the area, into its core. With the lack of fusion power, the result is a body of mass with a gravity too high to allow even light to escape. Scientists refer to this phenomenon as a black hole.