Do your research. When attempting to explain a black hole, you must study the basic laws of physics as well as Einstein's general theory of relativity.
Start with the basics. It helps to illustrate a picture of what a black hole looks like to help your audience grasp the concept. In general, a black hole can be visualized exactly the way it sounds: a black hole. Surrounding the black circle will be a ring of gas, dust and possibly stars. Picture thousands of bright specks swirling around the black center.
Define the black hole. A black hole can be described as an infinitely dense region in space where the force of gravity is so strong that it prevents any nearby matter from escape. Everything within a certain distance, including light and stars, gets sucked into a black hole.
Discuss the possible implications and current theories that surround the existence of black holes. For example, because it is unclear what happens to matter once it is sucked into a black hole, we cannot be certain that the conservation of mass applies.
Explain the continued research that is being done on the subject. Physicists are learning more about black holes each day by recording radiation data emitted by nearby matter.