Are Black Hole Objects Really Black Holes?

Crid ina: Are black holes actually black holes, like the sense of the concept of a black hole that einstein helped figure out? Or maybe ther could be something else that acts like something that could be a black hole. And so i think it's useful to let catalogue exactly what we do know about these objects that we've been calling black holes. But maybe it's really just the ex husband, or an ex black hole husband.