Diving: I Don’t Understand Roundabouts

This is embarrassing to admit, but I have to admit it to actually learn. I for the life of me just can’t seem to understand roundabouts. I’m in my early 20s, still with just my learner’s permit, and I am only comfortable regularly driving to and from work, the store, and a few other places. I still fear the highway (though not nearly as much as I used to) and I absolutely just feel incapable of understanding what to do at a roundabout. Can someone explain it to me? My mom always tells me that I have to stay in my lane and that I keep leaving it and that I don’t know where I’m going…but I don’t know how to know where each lane even ends up. I don’t know when or where I can ever leave the circle, and I just feel disoriented the second I enter one, like I’m either just stuck going in the circle forever or will inevitably just leave at the wrong place. Please, what am I not getting? I’m so lost- because I don’t even understand what I’m not understanding. What am I supposed to be seeing to understand what to do and where to go? Any advice?