What is money? Why paper and numbers have value

Money is whatever people in a society widely accept in exchange for goods, services and debts. It does three jobs: it pays for things, it measures what things are worth, and it stores value for later. Over history it has been shells, grain, gold and paper; today most money is simply numbers in bank accounts, and it has value because people trust that others will accept it.

In short

• Money is defined by what it does: medium of exchange, unit of account and store of value.
• Modern money is fiat money: not backed by gold, but by law, by trust in the institutions behind it, and by the taxes governments demand in it.
• Most money is not cash but bank deposits, and most of those are created when banks make loans.

What are the three functions of money?

The Bank of England lists the three jobs that make something money.

A medium of exchange is what people hand over to buy things. Without it, trade is barter: a baker who wants shoes must find a shoemaker who wants bread, at the same time. Economists call this the problem of the "double coincidence of wants". Money breaks the trade into two halves: sell bread for money, then buy shoes with it.

A unit of account is the yardstick prices are written in. With money, a market of 100 goods needs 100 prices. In barter, every good would need a price in terms of every other: 4,950 exchange rates for 100 goods. A common unit makes comparing, budgeting and keeping accounts possible.

A store of value lets someone earn today and spend next year. Money is not the only store of value, and not always a good one: when prices rise quickly, as explained in the note on inflation, money loses value, and people move savings into goods, property or foreign currency.

How did money develop?

Money has taken four broad forms, and each still exists in some way.

Kind	What it is	Why people accept it	Examples
Commodity money	A useful or rare object	The object itself has value	Grain, salt, cowrie shells, gold and silver coins
Representative money	A paper claim on a commodity	It can be swapped for the commodity	Goldsmiths' receipts, banknotes under a gold standard
Fiat money	Notes and coins the state declares money	Law, trust and the need to pay taxes in it	Today's dollar, euro, pound and yen
Bank money	A balance a bank owes its customer	It can be paid out as cash or sent to another bank	Checking and savings accounts

Coins of gold and silver alloy were struck in Lydia, in today's Turkey, around 2,600 years ago. China used paper money from the 11th century. In 17th-century London, goldsmiths began giving receipts for gold left with them, and the receipts started to circulate as money in their own right, the forerunner of banknotes. Under a gold standard, a note was a promise to pay a fixed weight of gold, which is why gold held its special place. The Bank of England's notes stopped being swappable for gold in 1931. The last link between the dollar and gold, for foreign governments, ended in 1971.

Why does paper money have value?

A $20 bill costs only cents to print. It is worth $20 because everyone expects everyone else to accept it for $20 worth of goods. That shared expectation rests on three supports. The law makes it legal tender for debts. The government demands taxes in it, so everyone who owes taxes needs it. And a central bank, such as the Federal Reserve, is charged with keeping its value steady by controlling interest rates.

Money is a kind of trust that has been made easy to pass on. When the trust fails, so does the money. In Zimbabwe in 2008 and Germany in 1923, governments printed so much that prices doubled in days and people stopped accepting the currency, falling back on foreign money or barter.

Where does most money come from? A worked example

Most money is not cash. The Bank of England says about 96% of the UK's money is held electronically as bank deposits and about 4% as notes and coins. In the United States, currency was about $2.4 trillion of the $23.4 trillion counted in the broad money measure M2 in September 2026, about 10%, according to the Federal Reserve's H.6 release.

Those deposits are mostly created by banks when they lend. The Bank of England's 2014 paper Money creation in the modern economy puts it plainly: "the majority of money in the modern economy is created by commercial banks making loans." Follow one loan:

1. Maya asks her bank for a $20,000 car loan and is approved.
2. The bank does not hand over anyone else's savings. It types $20,000 into Maya's account. Its books now show a new asset, Maya's promise to repay $20,000, and a new liability, the $20,000 deposit it owes her.
3. At that moment, $20,000 of new money exists that didn't exist before.
4. Maya pays the car dealer. The deposit moves to the dealer's bank. It is still $20,000 of money, now in someone else's hands.
5. Over five years, Maya repays the loan. Each repayment cancels part of her deposit and part of the debt. When the loan is paid off, the $20,000 she borrowed has gone out of existence; only the interest she paid remains with the bank.

Banks can't create money without limit. They need borrowers who want loans and are likely to repay, they must hold enough capital under banking rules, and, above all, the central bank's interest rate sets the price of borrowing. The same paper says the amount of money created "ultimately depends on the monetary policy of the central bank."

Still argued

Economists agree that bank lending creates deposits, but argue about how much that matters. Some, following the Bank of England's paper, stress that it overturns the textbook picture of banks lending out savings. Others reply that the textbook view and this one lead to similar conclusions in practice, because central banks still steer the total through interest rates and rules. Separately, supporters of cryptocurrencies such as Bitcoin argue that money with a fixed supply, outside any government's control, would be more trustworthy; most economists answer that its price swings too much for it to work as a unit of account or a steady store of value.

What does this mean for everyday life?

The money in a bank account is a promise: the bank owes it to the holder. Deposit insurance, up to $250,000 per depositor, per bank, for each type of account ownership in the United States, exists so that the promise holds even if a bank fails. The value of that money depends on what it can buy, which is why inflation, interest rates and the central bank matter to anyone with savings or debts. Money sits at the center of economics: almost every price, wage and plan is written in it.

Check yourself

• Name money's three functions and give an example of each from your own week.
• Why is a $20 bill worth $20, when it costs cents to make?
• Walk through what happens to the money supply when a bank makes a loan, and when the loan is repaid.

Sources

• What is money? — Bank of England
• Money creation in the modern economy — Michael McLeay, Amar Radia and Ryland Thomas, Bank of England Quarterly Bulletin, 2014
• Money stock measures, H.6 — Board of Governors of the Federal Reserve System, 2026
• Nixon ends convertibility of US dollars to gold — Federal Reserve History