Don’t worry anon, it’s fine! Butts are often hard to draw, so I’ll try to give you some refs.
First, under the fat covering every butt cheek are 3 very important muscles, the Gluteus medius, Gluteus maximus and Gluteus minimus. If properly trained, they can be very strong, but they will never (or almost never) be neatly defined like arm muscles or abs can be, because of the fat covering them.
At best, the butt will look round and smooth (you just have to Google “fine butt” to see what I mean, but I’m sure you already know).
Usually, it can be hard to know how to draw the limit between the butt and the thigh. The Gluteus maximus is attached to the femur, which means that the butt should not be drawned as a “C” (profile view) because the line doesn’t go back up. It’s more like half a circle, a round arch. A butt is either flat or round (or something in between), not “C” shaped. The firmer the butt, the clearer the point where the thigh begins.
There are as many types of butts as individuals. Some features can be found in some people, some others in some other people. For example, see this (detail of a photograph of Roberto Bolle by Bruce Weber):
Those dimples in green, at the base of the hips, well, not all people have them. Same for the slight crease formed on the side of the butt, in orange. If this is the proof that the muscles are strong, you can find strong butts without it.
That’s for the theory. For the practice, you should see this tutorial: How to Draw a Damn Fine Ass. A piece of wisdom if you’re struggling with booties.
I hope it helped somehow!