This is space-time squeezed in on itself. Schwartzschild radius depends on mass of black hole for the size of the event horizon . For the person going into a black hole, the feet would be stretched first because of tidal forces. Friction would cause heat and x-ray production. Black holes are black because gravity is so strong.
Gravity is strong because mass is high for very small object.
It appears as a band fuzzy light across the sky. Galileo was the first to resolve it into individual stars. Temperature and size are just right to make the star unstable for awhile. Expansion and contraction. RR Lyrae stars have periods of 0.5 to 1 days and are about 100 times brighter than the sun.