Final answer:
The inside of a black hole is a singularity, a point of infinite density and zero volume. Matter falling into a black hole appears to freeze at the event horizon, the boundary beyond which nothing can escape, but an observer riding on the infalling matter would pass through the event horizon.
Step-by-step explanation:
The inside of a black hole is a subject of great theoretical interest in physics. According to current theories, black holes have a singularity at their center, which is a point of infinite density and zero volume. Matter falling into a black hole appears to freeze at the event horizon, the boundary beyond which nothing can escape. However, if we were riding on the infalling matter, we would pass through the event horizon.