The black hole, because of its incredibly strong density, curves the spacetime a lot, until a point where there is no more space and time. There is a singularity. Like our experiment shows, the biggest the star is, the more the spacetime curves itself. But we don’t know a lot of things about black holes, a lot are just theoric. We have information on only 3 of their properties : their mass, their electric charge and their cinetic moment ( if they are in rotation or not). We also know that the entropy of a black hole is infinite. The entropy is a measure of the numbers of possibles configurations of the microscopic elements. the global entropy augments with the time because the surface of the black hole gets bigger. This really strong entropy would come from the transition of a complex object, the original object (like a star), to an object so ‘simple’ that it is characterised by only 3 factors. There are a lot of different theories in the world about the inside of this unknown celest body. There are also theories about the spacetime going in the other way on the other side of the black hole. That would mean that the spacetime curves in the other direction.