"Yeah, I can try to explain. But it's a lot, and I'm being a bit lazy, so I might make mistakes."
"In societies where the quiz writer is from, there's only one kind of person, and it's humans. Humans can't swear oaths. So nobody can be as powerful in a human society as Melkor is in Angband. So there are lots of interactions between humans in which they have things other people want, and other people have things they want, but nobody can just order the other person to give them the thing."
"When human societies are simple and small, they can resolve this by just trading things directly, or by owing each other favors, or such. But when there's lots of people, that gets pretty complicated. So people go 'Well, lots of people like having copper, and pieces of copper of the same weight are probably all similarly valuable. What if we used pieces of copper of the same weight to conduct exchanges? Then it will be less confusing, and even if I don't personally need copper for anything I'll probably be able to buy something from someone else with it later.'"
"This is a bit of a just-so story, I don't actually know what the introduction of money was like. The point is, money is a thing lots of people want that can be exchanged for stuff like food and apartments."