Money is a generally accepted medium of exchange, a unit of account, and a store of value. It acts as the standardized tool that allows individuals and businesses to trade goods without relying on direct barter.
Most people picture physical cash when they think of money, but modern currency is primarily digital credit. Understanding what is money functions are and how its supply expands is critical because it dictates what your savings can actually buy in the future.
This article covers money's core functions, how commercial lending creates it, and how the central bank influences its value over time.
Quick Takeaways
- Most modern money is not physical cash printed by the government, but digital credit created by commercial banks when they issue loans.
- Money serves three mechanical functions: it acts as a medium of exchange, sets a standard unit of account, and provides a store of value over time.
- Today's fiat currency holds value purely through government decree and public trust, not because it is backed by physical commodities like gold.
- When the supply of money expands faster than the real economy's output, it dilutes purchasing power and drives inflation.
What Is Money? (The Three Core Functions)
Money is an economic tool that solves the inefficiencies of barter by fulfilling three specific roles: a medium of exchange, a unit of account, and a store of value. Without it, economies face the "coincidence of wants": a farmer who wants shoes must find a shoemaker who specifically wants wheat.
To solve this, money provides three primary utilities:
- Medium of Exchange: It is an intermediary instrument universally accepted in trade. You can sell your labor for money, knowing you can trade that money for groceries later.
- Unit of Account: It provides a common measure to price all goods and services. Instead of pricing a car in terms of how many cows it equals, everything is measured in a standard currency unit, allowing for clear economic calculation.
- Store of Value: It allows you to save the purchasing power you earned today and spend it in the future. While inflation erodes this over time, a functioning currency must hold its value reasonably well from day to day.
How Money Is Actually Created (The Mechanism)
The vast majority of money in the modern economy is created out of thin air by commercial banks when they issue new loans, not by the government printing physical bills. When you understand this mechanism, the financial system becomes much clearer.
Economists divide the system into different layers. Narrow money refers to the highly liquid base layer of physical cash in circulation and the electronic reserves held by banks at the central bank. However, this is only a fraction of the total purchasing power in the system.
The rest is broad money, which includes all the digital deposits held by consumers and businesses.
When you take out a mortgage to buy a house, the bank does not take someone else's savings and hand them to you. Instead, the bank simply types digits into your account, creating a brand-new deposit, while simultaneously recording your mortgage as an asset on its balance sheet.
This act of lending instantly expands the total money supply in the economy. Conversely, when you pay down the principal on that loan, the digital money is destroyed, and the supply shrinks.
Metrics like the M1 money supply track the most liquid forms of this credit, such as checking accounts and physical currency, giving economists a real-time view of how much immediate spending power exists in the system.
Fiat vs. Commodity Money: The Role of Trust
Modern economies operate on fiat money, meaning the currency has no intrinsic value and is not backed by physical assets, unlike historical commodity money.
For centuries, money was backed by tangible commodities, primarily gold and silver. Under a gold standard, paper currency was essentially a receipt, theoretically redeemable for a fixed amount of physical metal.
This system physically constrained how much money a government could create. However, global economies progressively abandoned these constraints, culminating in the complete suspension of the dollar's convertibility into gold in 1971.
Today's fiat money relies entirely on trust. It holds value for two mechanical reasons:
- Legal Tender Laws: Governments decree that the currency is the only acceptable medium to pay taxes and settle debts.
- Network Effects: You accept the currency as payment today because you trust that everyone else will accept it from you tomorrow.
Because fiat money is not bound by physical scarcity, its total supply is limited only by central bank policy and commercial bank lending standards.
What the Money Supply Impacts (Purchasing Power & Inflation)
Expanding the money supply directly impacts your purchasing power, because creating more currency units without a proportional increase in real goods dilutes the value of each existing unit.
The quantity theory of money provides a classical framework for this relationship, often summarized by the equation $M \times V = P \times Q$. It states that if the money supply ($M$) increases, overall price levels ($P$) will also rise, assuming real economic output ($Q$) and the velocity of money, the rate at which money changes hands, remain relatively stable.
When banks create vast amounts of new credit, or when central banks inject severe liquidity into the system, more money ends up chasing the same supply of goods, services, and assets. This transmission mechanism drives inflation. For individuals, this means holding idle cash carries a structural risk over long periods: as the money supply expands, the real goods your savings can acquire mechanically shrink.
Common Misreadings: Does the Central Bank Print Everything?
A common misconception is that the central bank prints all the money in the economy, but it actually only controls the base layer of reserves, while commercial banks create the vast majority of circulating money.
Central banks use tools like open market operations to buy or sell government bonds, which mechanically adds or removes bank reserves from the financial system. These reserves are the exclusive digital money that banks use to settle payments with one another; consumers cannot spend them at a grocery store.
Historically, this relationship was taught through the money multiplier, suggesting that for every dollar of reserves, banks would mechanically lend out a fixed multiple based on reserve requirements. In modern, abundant-reserve banking systems, this constraint has shifted.
Banks lend based on profitable opportunities, borrower creditworthiness, and their own capital constraints, rather than being strictly gated by how many reserves they hold at the central bank.
Conclusion
Money is fundamentally a ledger of trust and credit. While it serves as a medium of exchange, a unit of account, and a store of value, the mechanical reality is that most modern money is created dynamically by commercial banks when they issue loans.
Because fiat currency is unbacked by physical commodities, its purchasing power is heavily dependent on how carefully the total supply is managed relative to the economy's output. To understand how the system's baseline cost of credit is managed at the top level, read about what is the federal reserve.