Crypto & TokensExplainer
What is bitcoin, and how does it actually work?
Bitcoin is a digital currency run by a network of computers instead of a bank. Learn how transactions, mining and the 21 million cap work, and the risks.
Quick answer
Bitcoin is a digital currency that launched in 2009 and runs on a public blockchain kept by a network of computers rather than a bank. New coins are created on a fixed schedule that approaches 21 million in total. Its price is highly volatile, and lost keys cannot be recovered.
Key points
- Bitcoin was designed so that payments could go directly from one party to another without a financial institution in the middle.
- Ownership is controlled by private keys; transfers are recorded on a public blockchain that anyone can inspect.
- New bitcoins are paid to the miner who adds each block; the reward halves every 210,000 blocks, so total supply approaches but never exceeds 21 million.
- In the U.S., the CFTC treats bitcoin as a commodity, and the SEC chair called it primarily a speculative, volatile asset when spot bitcoin ETPs were approved in 2024.
- Owning bitcoin brings price, custody and fraud risks that bank deposits and most funds do not have.
What is bitcoin, in plain English?#
Bitcoin is a digital currency with no central bank or company behind it. The U.S. Commodity Futures Trading Commission (CFTC) calls bitcoin a convertible virtual currency — a digital representation of value that functions as a medium of exchange, a unit of account and/or a store of value[1]. Convertible means it can be exchanged for ordinary money such as dollars.
The idea comes from a white paper by an unknown author using the name Satoshi Nakamoto. Its first sentence sets the goal: a purely peer-to-peer version of electronic cash would allow online payments to be sent directly from one party to another without going through a financial institution[2]. The Federal Reserve Bank of Chicago notes that bitcoin launched in 2009 and that its principles are attributed to an otherwise unknown Satoshi Nakamoto[3].
Bitcoin's rules in five numbers
How does a bitcoin payment work?#
There are no coins or files that move. The white paper defines an electronic coin as a chain of digital signatures: each owner transfers the coin to the next by digitally signing a hash of the previous transaction and the public key of the next owner[2]. In plain words, you prove you control the coins by signing with your private key, and you name the recipient by their public key or address.
The Chicago Fed's primer compares the key pair to sending someone a padlock to lock an item while keeping the key that opens it[3]. If you want the mechanics of signing and keys, read the private key definition. Every confirmed payment is then written into a shared ledger — the blockchain — described in how blockchains work.
That ledger is public. The white paper says the public can see that someone is sending an amount to someone else, but without information linking the transaction to anyone[2]. Addresses are visible; names are not attached to them by the network itself. That is privacy by pseudonym, not invisibility.
Where do new bitcoins come from?#
New bitcoins are created as a reward for adding blocks to the ledger, a job called mining. The white paper explains that, by convention, the first transaction in a block is a special transaction that starts a new coin owned by the creator of the block[2]. It compares this steady issuance to gold miners expending resources to add gold to circulation[2].
The Chicago Fed describes the schedule: the reward was initially 50, and it is halved every 210,000 blocks — about every four years at six blocks per hour — so the total number of bitcoins will approach but never exceed 21 million[3]. Halving events are often just called "halvings". We worked out what that rule implies, era by era.
Worked example
Worked example: what the halving rule implies for supply
Each era lasts 210,000 blocks, which at six blocks per hour is 35,000 hours, or about 3.99 years. New coins in an era = 210,000 × the reward. This is the pure rule; the real software rounds to tiny units, so actual totals differ very slightly.
| Era (210,000 blocks each) | Reward per block | New coins in era | Total issued by end of era | Share of 21 million |
|---|---|---|---|---|
| Era 1 | 50 | 10,500,000 | 10,500,000 | 50.00% |
| Era 2 | 25 | 5,250,000 | 15,750,000 | 75.00% |
| Era 3 | 12.5 | 2,625,000 | 18,375,000 | 87.50% |
| Era 4 | 6.25 | 1,312,500 | 19,687,500 | 93.75% |
| Era 5 | 3.125 | 656,250 | 20,343,750 | 96.88% |
Figures computed in code from the stated inputs; rounded to the nearest cent or tenth.
Bitcoin issued under the halving rule
A fixed schedule does not make the price stable. Supply is predictable; demand is not. The price is set by whatever buyers and sellers agree on each moment.
Is bitcoin a currency, a commodity or an investment?#
It depends who is asking and where. In the U.S., the CFTC says virtual currencies such as bitcoin have been determined to be commodities under the Commodity Exchange Act[1]. Rules differ by country, and some countries treat bitcoin very differently.
When the SEC approved the first spot bitcoin exchange-traded products in January 2024, its then-chair stressed that the agency did not approve or endorse bitcoin, and described bitcoin as primarily a speculative, volatile asset[4]. People do use bitcoin to make payments. This note treats it as an asset whose price can swing widely, which is why it belongs in an investing discussion of risk and return.
What are the main risks of owning bitcoin?#
The CFTC's undated Bitcoin Basics primer warns that the virtual currency market overall is largely unregulated — U.S. rules have changed since, so read that as a caution rather than a current survey — and lists three practical dangers: virtual currencies are commonly targeted by hackers and fraudsters, have no assurance of recourse if stolen, and involve e-wallets or storage that present cybersecurity risks[1]. Its customer advisory adds that their value is derived entirely from supply and demand, making them more volatile than traditional currencies[5].
| Risk | What it means in practice |
|---|---|
| Price volatility | Large, fast moves in either direction; there are no earnings or interest to anchor value |
| Lost or stolen keys | If your private key is lost, access is permanently gone; stolen coins usually cannot be recovered |
| Platform failure | A company holding your coins can be hacked, shut down or go bankrupt |
| Fraud | Fake platforms, impersonators and "investment" pitches target crypto owners |
| Thin protections | Crypto accounts are not covered by FDIC deposit insurance or SIPC |
Sources: CFTC[1][5]; SEC custody bulletin[6]; SEC investor alert on SIPC/FDIC[7].
The SEC's custody bulletin is blunt about keys: if you lose your private key, you permanently lose access to the crypto assets in your wallet[6]. For the full list — including scams — read the risks of crypto investing. For how price swings are measured, see volatility.
How do people get exposure to bitcoin?#
There are three common routes in the U.S., each with different trade-offs. None is risk-free, and none changes how volatile bitcoin itself is.
| Route | Who holds the keys | Main extra risk |
|---|---|---|
| Buy on a crypto platform and leave it there | The platform | The platform is hacked, shuts down or goes bankrupt |
| Buy and move it to your own wallet | You | You lose the key or recovery words, or are tricked into sending it |
| Buy shares of a spot bitcoin ETP through a broker | The product's custodian | Sponsor fees, and the share price can differ from bitcoin's price |
The SEC notes spot bitcoin ETPs may give exposure without some direct risks of using a crypto platform or wallet, but they pay a sponsor fee[8].
If you are comparing routes, our explainer on spot bitcoin ETFs walks through how those products work. Whatever the route, the size of the position matters more than the route itself — see diversification.
What mistakes do beginners make?#
Treating the 21 million cap as a price floor
A limited supply says nothing about demand. Prices can fall a long way even when supply is fixed.
Keeping recovery words online
Photos, cloud notes and emails of recovery phrases are a common route for theft. Anyone with those words can take the coins.
Confusing the network with the platform
The Bitcoin network can keep running while the company holding your coins fails. Know who holds your keys.
Believing anyone who promises fixed bitcoin returns
Fixed or very high promised returns on bitcoin are a classic fraud pattern. The CFTC states there is no such thing as a guaranteed investment or trading strategy[5].
What else do beginners ask?#
Who controls bitcoin?
No single company or government issues it. Under the white paper's design, nodes follow the chain with the greatest proof-of-work effort behind it[2] rather than instructions from a central operator. That does not mean the price is free from influence by large traders or platforms.
Is bitcoin anonymous?
Not fully. The white paper says the public can see that someone is sending an amount to someone else, without information linking the transaction to anyone[2]. Addresses and amounts are public; if an address is ever tied to your name, its history is too.
What happens when all 21 million bitcoins are issued?
Under the rule described by the Chicago Fed, the reward keeps halving, so issuance shrinks toward zero rather than stopping suddenly[3].
What is the bottom line?#
Bitcoin is a digital currency run by a network instead of an institution, with a public ledger and a supply schedule that approaches 21 million. Those rules are clear; its price is not. Understand how keys, platforms and volatility could cost you money before deciding whether bitcoin has any place in your plans.
Sources
Numbers in brackets in the text point here. Grade A = primary source (regulator, statistics agency, law or official document).
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