A black hole and a nebula are totally different things. There is nothing similar in a nebula and a black hole. This is a nebula In essence, a nebula is formed when portions of the interstellar medium undergo gravitational collapse. read more
A black hole is an intense area of gravity that doesn't allow anything to escape its pull including light. See definitions below. A nebula (Latin:"mist"; pl. nebulae or nebulæ, with ligature) is an interstellar cloud of dust, gas and plasma. read more