Bitcoin
From "magic internet money" to genuinely understanding the machine — block by block.
How Bitcoin actually works — the public ledger and mining, proof-of-work, the 21-million cap and halvings, keys and wallets, sending a transaction and its fee, full nodes, and the Lightning Network — all from zero.
You already know what a blockchain is — a shared, append-only ledger a crowd of strangers keeps honest without a boss. Bitcoin is the first and most famous machine built on that idea, and this topic opens it all the way up — no hand-waving, no assuming you’ve ever owned a satoshi.
We build it as a ladder, eight rungs at a time:
- What Bitcoin is and why it exists — the problem it was designed to solve.
- The ledger and mining — the machinery that keeps it running.
- Proof-of-work — the race that decides who writes the next page.
- The 21-million cap and halvings — why supply is fixed and what cuts the flow of new coins.
- Keys, addresses and wallets — the part that’s actually yours, and why “not your keys, not your coins” is the whole game.
- A transaction and its fee — following one from your screen to a confirmed block, and where the fee goes.
- Full nodes — the ultimate “don’t trust, verify.”
- The Lightning Network — Bitcoin’s answer to buying a coffee without waiting ten minutes.
Get these eight and Bitcoin stops being a vibe and starts being mechanics.
In this topic
- 1 What Bitcoin Is and Why It Exists Bitcoin from zero: decentralized digital money with no bank, no central issuer, and a fixed 21-million supply — the problem it solves and the myths it doesn't deserve. 8 min
- 2 The Ledger and Mining How Bitcoin's blockchain grows: the mempool of pending payments, miners batching them into blocks every ~10 minutes, the block reward and fees that pay them, and the difficulty retarget that keeps the clock steady. 9 min
- 3 Proof-of-Work: How the Winner Is Chosen The mining lottery explained: grinding nonces to find a hash below target, why work is hard to do but easy to verify, the longest-chain rule, hashrate, and what a 51% attack can and cannot do. 9 min
- 4 The 21-Million Cap and Halvings Why there will only ever be 21 million bitcoin: the block subsidy that halves every 210,000 blocks, the geometric series that sums to 21M, satoshis and divisibility, and what happens when the subsidy hits zero around 2140. 8 min
- 5 Keys, Addresses, and Wallets Who really owns a bitcoin: the private key that signs, the public key and address derived from it, the seed phrase that backs up everything, and why 'not your keys, not your coins' is the whole game. 9 min
- 6 Sending a Transaction and Its Fee Follow a bitcoin payment from your screen to a confirmed block: inputs and outputs, the change you send back to yourself, the mempool fee market in sat/vByte, confirmations, and why a fee is paid to the miner — not to a company. 9 min
- 7 Nodes and Full Verification Don't trust, verify: what a Bitcoin full node actually does, how it enforces consensus rules and rejects invalid blocks even from miners, the difference between nodes, miners, and light wallets, and why thousands of nodes make Bitcoin censorship-resistant. 8 min
- 8 The Lightning Network at a Glance Bitcoin's answer to buying a coffee: payment channels that lock funds on-chain once, then settle thousands of instant, near-free payments off-chain, routed across a network of channels — and the trade-offs that come with it. 8 min
- 9 Final Exam: The Bitcoin Gauntlet A graded, locked capstone exam — 26 one-shot questions across every Bitcoin lesson: what Bitcoin is, the ledger and mining, proof-of-work, the 21M cap and halvings, keys and wallets, transactions and fees, full nodes, and the Lightning Network. 16 min
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