Some people actually find that this works out for them pretty well.Often people find that if they just follow this script then it’s easier because they don’t have to talk about it.
There are, of course, lots of different kinds of sex that people find more enjoyable – more about this here.It can mean who is ‘on top’ in a sexual position (confusingly the person ‘on top’ could also be penetrated from the person on ‘the bottom’).It can also be about who is more active or passive – either for one specific bit of sex, for the whole sexual encounter or for the whole relationship. The simple explanation often found on that internet is that this is a term used by gay men to determine who is going to put their penis (the top) inside the anus of the other (the bottom).
Buuuut it can also be a term that people use about different kinds of sex too and this doesn’t just apply to gay men (who often don’t like anal sex actually).
As you can see a lot of this stuff is based on some pretty big assumptions and stereotypes that you might not agree with. The man, the most masculine, the person with the penis, the dominant one, the more confident one or the one who has done it before will be the top or will ‘top’.