Money or currency is a way to represent value

It is a medium of exchange

Could your boss pay you in cows? Could you take those cows and trade them for a car? Yes but this would be difficult.

So if your boss gave you a cow voucher “money” and you could trade that for a car, then you wouldn’t have to lug the cows around.

It facilitates trade

Why a US dollar, or another currency, has value is a whole other question

Sounds like you need to read the book Debt: the first 5000 years by David Graeber.

Money is a transferrable form of debt, and debt is emotion. You do something for someone or give someone something. They are then “indebted” to you. Or the reverse - you’ve been issued a fine, meaning some of the “debt” others owed to you for something valuable is now void because you did something interpreted negatively.

The physical money symbolizes the feeling of indebtedness, and standard currencies allow people to recognize one anothers’ debts as something commonly valuable and transferrable for symbolizing new debts.

It sounds kind of like karma, but because money is just symbolic for debt and not actually the real manifestation of the emotions associated with the causes of the indebtedness, having a lot of money, or vice-versa, doesn’t translate to a karmic judgment of a person. Someone can trick their way into making others feel indebted to them, at least at the point in time of the emotion to money exchange. Or, they can literally steal the “debt markers” that others accrued. Or, one can decide that one kind of debt is not worth as much as another kind of debt - foreign exchange rates, employment wages, etc mediate this mostly in the sense that human time is not valued identically depending on where a person lives or who they are.

And you can be “wealthy” without money, as long as enough people feel indebted to you and you can “exchange” that indebtedness for the things you want. The money is just for easy debt accounting and transfer.

At one time, it was a government promise to exchange for a certain amount of gold. After that became a limit on growth of a nation it becomes “fiat currency” which is simply a conceptual agreement of value to make the exchange of goods and services easier. This is your AMEX money.

Money is a promise given to you that someone else will be ready to give you something you want if you give money to them.

And you trust the money to be useful when you need to make other humans do stuff, it can be giving their time or owning something that you didn’t own before.

Money itself don’t have any value, it’s a pointer to anything of value. Without money it would be very hard to know exactly how rare is rice compared to sweater. But now using money you can know that you require same amount of human efforts for bringing 70 kg of rice as 1 pcs of sweater to the superstore.

https://youtu.be/-nZkP2b-4vo

This was a pretty good series on the subject. He goes into what “currency” is right at the beginning

One answer: The ability to pay taxes to the largest local military power, in exchange for keeping a ‘good’ relationship with the legal system it operates with.

Another: a tool for coordination and distribution of resources between large groups of people that does not require very many (or very long) meetings.

I like a lot of what other people have said here (faith backed by a trusted party, representation of debt, etc), but I just want to drive home the point that money has value because we said it has value. Under a system of barter, you end up with people valuing things differently. So we switched to the gold standard, but then that constrained growth. Now we have fiat currency which is based on faith.

The reason why we chose gold was because it was relatively useless at the time, only good for making things look pretty essentially. It was valuable because it was rare, and since it was rare, a central authority could control the supply because it takes a lot of capital to extract and process. Modern fiat is similar, but the rarity (making it a good substitute for value of other goods and services) comes from the government being the only person who can issue it. It’s honestly kind of a weird paradox. It has to be cheap and ubiquitous enough that the supply isn’t limited, but rare enough that we accept it as a stand in for value. In an alternate universe, we could have chosen river rocks (not useful for other purposes, so no one would be tempted to take supply out of the system to use for other means, and pretty ubiquitous), but we couldn’t effectively control the supply.

It’s supposed to be a way of representing the value of goods and services. But when some people posses a hoard of billions of these imaginary units, I question their usefullness at symbolically representing goods and services

Money has value because everyone believes it does.

(Which also applies to cryptocurrency, despite what some of its promoters seem to believe)

Which is the same as any other thing that has value, really ; food only has value because you believe staying alive has value.

Enough people who have goods or can provide valuable services agree to use it and something limits the amount of it in circulation.

it’s currently the best alternative we’ve found to bashing each others heads in when someone else has something we want