What exactly is gaslighting?

I originally thought that gaslighting was very simply when an abusive person (friends or family) tries to convince you that you're going insane or that you have some sort of memory disorder, when neither are actually true.

When I was a kid, I once got a memory test and my mom tried to say that my doctor said that I have an Alzheimer's like memory disorder to her on the phone, and that she needs to make sure that I'm around her more often. She would lie to me about random things and when I questioned her, she would plant false memories into my head. "No I said this, remember?" "That didn't happen honey, this is what happened." Later, I brought up my memory problems to my neurologist, in a way like this was something she should already know very well and she was like "You're memory test came back fine, you just have some executive functioning problems because of your ADHD." After that, I recorded my me and my mom's conversations and caught her in the act.

Ever since that, I just simply said that my mom gaslit me when I was a kid. That's much easier than explaining that whole thing to you. If I remember correctly, that's pretty much how it was defined by one of my teachers in high school when we talked about the different types of abuse. But in recent years I've heard people accuse their bosses of gaslighting them, I once heard a YouTuber say that his fans were gaslighting him in the comments, stuff like that. This confuses me, because when they explain it, it pretty much just sounds like lying, nothing like what I went through. This just makes me feel confused and like what I went through as a kid wouldn't be taken as seriously if I just explained what happened to me as simply "gaslighting".

I just don't really understand. These seem like completely different things to me. There must be something I'm not understanding.