The first person to develop the idea of black holes was the French mathematician Pierre Simon de Laplace. Laplace agreed with Isaac Newton that light is made up of particles. He theorized that if enough mass were added to a star, the gravitational force would become so great that its escape velocity would equal the velocity of light. When Einstein developed his special theory of relativity, he argued that nothing can move faster than light. This means that Laplace's black stars are also black holes, because if light can't escape, all other matter would be trapped also.
Many people believe that black holes suck everything within a million miles.
That is not true. Only if something gets to close to the event horizon will it get sucked up, but it won't get sucked up just then. It may orbit around the black hole for a couple of years and then get sucked up. There are two ways to identify black holes. One is to detect theoretical gravitational waves that could be given off just before the black hole is formed.