The short answer
Bitcoin is money whose rules nobody can change on their own. A fixed number of units, issued on a published schedule, moved by whoever holds the right key rather than by whoever runs the payment system. There is no company to appeal to, no administrator, and no customer service. That is the point, and it is also the price.
Two spellings, and they mean different things:
- Bitcoin, capitalised, is the network and the protocol: the rules, and the computers around the world that independently enforce them.
- bitcoin, lowercase, is the unit those rules issue. It divides to eight decimal places, and the smallest unit is one satoshi, a hundred millionth of a bitcoin.
If you stop reading here, that is the thing to keep.
Where it came from
In October 2008 somebody publishing under the name Satoshi Nakamoto posted a nine-page paper describing a payment system with no trusted third party, Bitcoin: A Peer-to-Peer Electronic Cash System. The first block was mined on 3 January 2009. Nakamoto stopped posting in 2011 and has never been identified.
Nothing about how Bitcoin works depends on who they were. That is unusual for money, and it is worth sitting with for a moment: there is nobody whose credibility the system rests on.
The four rules that do the work
1. Issuance is fixed and scheduled. New bitcoin come into existence only as a reward paid to whoever adds the next block of transactions, and that reward halves roughly every four years. It last halved at block 840,000 on 20 April 2024, from 6.25 to 3.125 bitcoin per block, which we covered in the fourth halving. Run that schedule forward and it sums to just under 21 million, with the last fraction issued around the year 2140. No vote changes it, because no vote exists.
2. Ownership is a key, not an account. You do not have a balance at an institution. You have a private key, and the only thing that can move coins is a signature that key produces. Anyone can verify the signature; nobody can work backwards from it to the key. That is the mechanism, and we take it apart in asymmetric cryptography.
3. The ledger is public and everybody keeps their own copy. Every transaction that has ever happened is written into a shared, append-only record: the blockchain. You do not have to ask anyone whether a payment happened. You can check.
4. Changing the rules means convincing everyone. Each computer running the software rejects anything that breaks the rules it holds, including blocks from the largest miner on earth. A change that most participants do not accept simply produces blocks that everyone else ignores.
Bitcoin and gold
Bitcoin is often called digital gold. The comparison is useful in a narrow way and misleading past that point.
| Bitcoin | Gold | |
|---|---|---|
| Supply | Capped at 21 million by protocol rule | Grows every year by whatever miners pull out of the ground |
| Moving it | A transaction anyone can broadcast, settled in an hour or so | Physically shipped and insured |
| Dividing it | To eight decimal places, at no cost | Assaying and recasting, with loss |
| Verifying it | Anyone with the software can check every unit | Requires an assay you have to trust |
| Holding it | A key you must never lose or leak | A vault, or a claim on someone else's vault |
Where the analogy breaks: gold exists whether or not anybody is watching, and it has industrial demand underneath its monetary use. Bitcoin exists only as entries in a ledger that a network keeps. If nobody ran the software, there would be nothing left. Gold also forgives a lost combination in a way a lost key does not.
Bitcoin and government currency
Government currency (dollars, euros, yen) is issued by a central bank and moved by regulated intermediaries. Both of those facts have consequences in both directions.
| Bitcoin | Government currency | |
|---|---|---|
| Who issues it | A fixed schedule in software | A central bank, at its discretion |
| Who can stop a payment | Nobody, once it is confirmed | The bank, the processor, or a court order |
| Settlement | Final after confirmation, typically within the hour | Reversible for days, sometimes months |
| Privacy | Pseudonymous and permanently public | Private from the public, fully visible to your bank |
| If it goes wrong | Nothing to appeal to | Chargebacks, deposit insurance, a regulator |
That last row is the honest tradeoff and it runs the other way from the rest. A bank can freeze your account, and a bank can also reverse the payment you were tricked into making. Bitcoin does neither. Choosing it means accepting that mistakes are yours to carry, which is exactly why the custody posts on this site are as insistent as they are.
What people get wrong
"Bitcoin cannot be seized." Coins move when somebody produces a valid signature. No government can freeze a balance remotely or reverse a confirmed transaction, and that is a real difference from a bank account. But a key can be stolen, copied, extorted from its owner, or lost. Self-custody moves the risk from an institution onto you. It does not delete it.
"Bitcoin is anonymous." It is pseudonymous, which is weaker than it sounds. Addresses are not names, but every transaction is public forever, and analysis firms are good at connecting addresses to people once one link is known.
"A fixed supply means the price goes up." A fixed supply is a statement about issuance, not about demand. It says what will not happen to the number of units. It says nothing about what anyone will pay for one. The price has collapsed hard enough to take large lenders down with it, more than once: that is what Celsius freezing withdrawals in June 2022 was the middle of.
Where to go next
- How Bitcoin works: the moving parts, and what happens between pressing send and the payment being final.
- How to choose a wallet: what a wallet actually holds, and the one question to settle before any other.
- Multisig setups: removing the single key that can lose everything.
- Inheritance planning: making sure the coins outlive you.