@Yetanotheruser While we can’t directly observe black holes, they are rather like the wind. We can’t see it, but we can measure and feel its effects. We can observe the effects of the supermassive black hole at the center of our galaxy. It gives our galaxy order and binds it together in its elegant spiral form with the noticeable bulge at its center. We can observe that there is a supermassive black hole at the center of many massive galaxies. There are some that do not have them. M33 is a large, nearby galaxy without a supermassive black hole. We are able to observe differences its lack causes.
We can also observe some smaller black holes left over from the gravitational collapse of a supermassive star. We cannot see the black hole itself, but we can see its gravitational effects on nearby objects and often detect massive radiation emissions from the heated gasses that swirl around its event horizon as they are sucked in.