In the video a Nasa guy talks about black holes. How are black holes formed, how they are during their life and how black holes die. Its basically the work of Stephan Hawking. In Stephan Hawking’s book the Brief History of time. He also talks about event horizon and how the death of a star leads to birth of a black hole.
A black hole is a region of spacetime where gravity is so strong that nothing — no particles or even electromagnetic radiation such as light — can escape from it.The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. Although it has an enormous effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe directly.
So black hole is basically a celestial body in the outer space and lies in the universe. Black hole has a very strong gravity such that even light is unable to escape it’s gravitational pull.