Money is a medium for exchange. It’s a great way to exchange known value to fill perceived needs.
Gold backed money, because the total quantity of gold is limited and it’s impossible to extract an infinite amount, is stable.
Fiat money, is issued by “authorities” any time they feel like it.
The US stopped backing the dollar with gold, because we didn’t have enough gold. No the US issues more dollars when they think it’s a good idea. But, let’s go back to the purpose of money: exchange known value. The problem with the US dollar, is it doesn’t have known value.