A digital payment, without a central account keeper.
A photo can be copied and sent to two people. Money needs a different rule: sending the same funds twice must not create two valid payments. Bitcoin coordinates a shared record of which funds have been spent and who can spend the remaining funds.
A wallet helps you prepare a transaction. A spending key authorizes it. Other computers check it against the network’s rules, rather than simply trusting the sender’s claim.
Follow one payment.
The sender signs a transaction and broadcasts it. Network nodes check that the signature is valid and the funds have not already been spent. Miners propose blocks of transactions; nodes independently check those blocks.
As valid blocks build on each other, reversing an earlier payment becomes harder. “Sent” and “confirmed” are different stages. A recipient chooses how much confirmation to wait for based on the payment and its risk.
One payment. Rules checked by many.
- SenderWallet signs a transaction with a spending key.
- Shared networkNodes check signatures and unspent funds. Miners propose blocks; nodes verify them.
- RecipientWallet sees the payment and its confirmations.
What people use it for.
You can pay someone who accepts bitcoin, transfer value to another person, or hold it for later. With self-custody, you control the keys that authorize spending. With a provider, you rely on that provider to act for you. We will compare those choices in lesson five.
Think of a friend paying you for a used bicycle. The useful result is a transfer you can verify—not a promise that the bitcoin will buy more bicycles next year.
The responsibilities travel with the money.
Base-chain transactions can take time and incur fees. Fees depend on the transaction and demand for block space, not simply the dollar value sent. A mistaken payment generally has no central help desk that can reverse it.
Price can fall, records are public, and key management matters. Bitcoin creates a way to transfer and hold value; it does not remove every cost, trust decision or source of risk.
Check your understanding
If you copy a wallet app onto another phone, have you doubled your bitcoin?
No. Both apps may refer to the same spending rights on the same shared ledger. Copying software does not create another spendable balance.
Sources & further reading
Reviewed 16 October 2026. Sources support the explanations; hypothetical examples and diagrams are labelled where they appear.
- Bitcoin.org: How does Bitcoin work?
Wallets, signatures, the shared ledger and mining.
- Bitcoin developer guide: Transactions
Technical explanation of transaction outputs and spending conditions.