Black holes are typically the condensed stellar remnants of supermassive stars that have reached the end of their lives. Nuclear fusion has ceased, and the star has collapsed into a singularity, where gravity is so extreme that light can no longer escape.
Black holes are relatively rare objects in the Milky Way galaxy and cannot be fuel scooped. Although they cannot be flown into directly due to their exclusion zones, they still present a minor hazard to travelers. In most cases, arriving in a system with a black hole will result in the pilot's ship almost immediately colliding with the exclusion zone and making an emergency drop into normal space. Aside from the disorientation and light damage this can cause, continuing to fly in the direction of the black hole instead of escaping will cause heat to slowly build up within the ship, potentially resulting in ship loss if the pilot is inattentive or suicidal.
Supermassive Black Holes
Supermassive black holes (SMBHs) tend to form when an initial black hole begins to swallow even more mass, including other black holes. They acquire an incredible amount of mass over time, on the order of hundreds of thousands to billions of solar masses. They are found in the center of almost all known massive galaxies, including the Milky Way. Sagittarius A* is the Milky Way's only known supermassive black hole, and behaves similarly to standard black holes.