A star collapses into a black hole because it has no power to support its shell after aging. Therefore, its core collapses gradually under the pressure of the shell, making its volume infinitely smaller, and finally forms a black hole. Black hole is a celestial body with strong gravity. We can't observe it directly for a long time. Why does a star collapse into a black hole? The reason why a star collapses into a black hole is that it will gradually age with the passage of time. In this way, it will lose the power to support its huge shell, so the core of the star will gradually collapse under the pressure of the shell.
This process will lead to the infinitely smaller volume of the star, and its density will infinitely increase in this process. Finally, the radius of the star will shrink to less than the Schwarzschild radius, and then it will almost become what we often call a black hole.
Black hole is a celestial body with strong gravity. Its space-time curvature is so large that even light can't escape. For a long time, human beings can not directly observe the black hole, but can only understand it by indirect means.