How Bitcoin Works
Bitcoin is not “an app” — it’s a global network that lets people transfer value without needing a bank. This page explains the moving parts in plain English: transactions, blocks, mining, nodes, and why it’s hard to fake.
📌 Sections
- 1) The 5 parts of Bitcoin (simple map)
- 2) Keys, addresses, and ownership
- 3) Transactions & the mempool
- 4) Blocks & confirmations
- 5) Mining & proof-of-work (why it’s secure)
- 6) Nodes & consensus (who enforces rules)
- 7) Fees, finality, and “why it sometimes costs more”
- 8) Fixed supply, halving, and difficulty
- 9) What can go wrong (and what cannot)
- 10) Next steps
1) The 5 parts of Bitcoin (simple map)
| Part | What it does | Why it matters |
|---|---|---|
| Wallet | Stores your keys (proof you own bitcoin). | Ownership is key control. |
| Transaction | A signed message that moves bitcoin from one owner to another. | Transfers value without asking permission. |
| Mempool | A waiting room where unconfirmed transactions sit. | Fees help decide what gets confirmed first. |
| Blocks | Batches of transactions linked together in time order. | Creates shared history for everyone. |
| Mining + Nodes | Miners propose blocks; nodes verify and enforce rules. | Rules stay predictable and enforceable. |
Think of Bitcoin as a rule-governed ledger: miners earn the right to write the next page, and nodes decide if the page is valid.
2) Keys, addresses, and ownership
- Private key: your secret. It authorizes spending.
- Public key: derived from the private key. Used to verify signatures.
- Address: a shareable destination (like an inbox). It points to where bitcoin can be sent.
A wallet doesn’t “hold coins” like a pocket. It holds the keys that can unlock spending rights recorded on the blockchain.
3) Transactions & the mempool
When you send bitcoin, your wallet creates a transaction that:
- references previous outputs you own (the “inputs”)
- specifies who receives it (the “outputs”)
- includes a fee for miners
- is signed with your private key
What is the mempool?
The mempool is a shared waiting area. Nodes relay valid transactions to each other. Miners pick from the mempool when building a block.
Why do fees exist?
Block space is limited. Fees help prioritize which transactions get included first — especially during busy times.
4) Blocks & confirmations
A block is a bundle of transactions plus a link to the previous block. These links create a chain: the blockchain.
- 1 confirmation = your transaction is included in a block.
- More confirmations = more blocks are built on top of that block.
5) Mining & proof-of-work (why it’s secure)
Mining is a competition to find a valid block by performing computational work. This work is called proof-of-work.
- Miners try many guesses (hashes) until they find one that meets the network’s target.
- The first miner to find a valid block broadcasts it to the network.
- Nodes verify the block. If valid, it becomes the next block in the chain.
What miners do
Miners propose blocks and earn rewards (block subsidy + fees) for securing the network.
What proof-of-work prevents
It makes attacks expensive. To rewrite history, an attacker must outspend the honest network’s power.
6) Nodes & consensus (who enforces rules)
A node is a computer running Bitcoin software that verifies rules:
- Are transactions properly signed?
- Are coins being spent twice?
- Are block rules followed (size, validity, subsidy, etc.)?
7) Fees, finality, and “why it sometimes costs more”
- Fees are paid to miners and measured in sats per byte (or sats/vB).
- When the mempool is crowded, higher fees tend to confirm faster.
- Finality increases with confirmations (practical finality for most use cases after multiple confirmations).
For instant, low-fee payments, Bitcoin uses Layer-2 systems like the Lightning Network (when appropriate).
8) Fixed supply, halving, and difficulty
Fixed supply
Bitcoin’s maximum supply is capped at 21,000,000 BTC. New bitcoin is issued on a schedule built into the protocol.
Halving
Roughly every four years, the new-coin reward per block is cut in half. This slows new issuance over time.
Difficulty adjustment
The network adjusts mining difficulty periodically to target a steady block rhythm. If miners add more power, difficulty rises. If power drops, difficulty falls.
9) What can go wrong (and what cannot)
| Risk | What it looks like | Best defense |
|---|---|---|
| User error | Sending to wrong address, losing keys, weak backups. | Self-custody discipline |
| Scams | Fake support, phishing, “send to receive more,” malware. | Verification + caution |
| Exchange risk | Withdrawals paused, insolvency, account freezes. | Withdraw to your wallet |
| Protocol rule break | Trying to create invalid coins or fake signatures. | Nodes reject invalid data |
| “Someone changes the rules” | Attempt to force a rule change without broad agreement. | Consensus is voluntary |
The most common failures are human-level (keys, scams, custody), not “Bitcoin got hacked.”
10) Next steps
Built in public. No hype — just clarity.