71 words the Bitcoin world throws around, explained in plain English. No jargon explaining the jargon.
The absolute basics
Bitcoin (big B) vs bitcoin (small b) — Big B is the network — the shared notebook. Small b is the coin that lives on it.
Blockchain — The shared notebook itself: every transaction ever, in order, copied across thousands of computers that check each other.
Block — One page of the notebook — a bundle of recent transactions, added roughly every 10 minutes.
Satoshi Nakamoto — Bitcoin's anonymous creator. Published the design in 2008, wrote the first code, vanished in 2011. Identity still unknown.
Whitepaper — The 9-page document from 2008 where Satoshi laid out the whole idea. Still readable by normal humans.
21 million — The maximum number of bitcoins that will ever exist. Written into the code; no one can raise it. The one big idea.
Satoshi / sat — The smallest unit of bitcoin — one hundred-millionth of a coin. You buy sats, not whole bitcoins.
Peer-to-peer (P2P) — Directly between two people, no company in the middle. Like handing someone cash, over the internet.
Decentralized — No headquarters, no CEO, no off switch. The network is run by everyone using it and controlled by no one.
Genesis block — The very first page of the notebook, created January 3, 2009. Satoshi embedded a newspaper headline about bank bailouts in it.
Money words
Fiat — Government-issued money — dollars, euros, yen — backed by trust and law rather than any physical thing. The 1971 story.
Inflation — Each unit of money buying less over time, usually because more units keep being created.
Store of value — Something you hold to move savings into the future — gold, real estate, and increasingly, bitcoin.
Hard money — Money that's genuinely difficult to make more of. Gold was hard because of chemistry; bitcoin is hard because of math.
Digital gold — The most common shorthand for bitcoin's role: scarce like gold, but weightless, divisible, and sendable anywhere.
Market cap — The price of one coin times all coins in existence. A rough measure of total size, not money actually invested.
Volatility — How wildly a price swings. Bitcoin's is famous — plan for it.
Bull / bear market — Bull: prices rising, everyone's a genius. Bear: prices falling, everyone's a philosopher.
Liquidity — How easily something converts to cash without moving the price. Bitcoin is among the most liquid assets on earth — it trades 24/7.
ETF — A fund that holds bitcoin so people can get price exposure in a normal brokerage account without touching the actual coins.
Stablecoin — A crypto token designed to track the dollar. Useful plumbing, but it's a company's IOU — the opposite of bitcoin's whole idea.
Altcoin — Any cryptocurrency that isn't bitcoin. Thousands exist; most are startups, experiments, or jokes wearing Bitcoin's costume.
Wallets & keys
Wallet — The app or device that holds your keys. It doesn't hold coins — those live in the notebook. It holds the pen. How sending works.
Private key — The secret that lets you spend your bitcoin. Whoever has it, owns the coins. Never share it. No exceptions, ever.
Public key / address — What you share so people can pay you — like an account number you generate yourself, free, no permission needed.
Seed phrase — 12 or 24 words that back up your keys. Written on paper, stored safely, shown to nobody. It IS the money.
Self-custody — Holding your own keys instead of trusting a company to. The point of the whole system.
Custodial — A company holds the keys for you (like an exchange). Convenient, but you own an IOU, not bitcoin.
Not your keys, not your coins — The rule that summarizes the two entries above. Exchange collapses have taught it the hard way, repeatedly.
Cold storage — Keys kept on a device that never touches the internet. Maximum security for serious amounts.
Hot wallet — Keys on an internet-connected phone or computer. Fine for spending money, not for savings.
Hardware wallet — A small dedicated device (looks like a USB stick) that signs transactions without exposing your keys to your computer.
Multisig — A setup requiring multiple keys to spend — like a safe deposit box needing two of three keys. Removes single points of failure.
How it moves
Transaction — An entry in the notebook: coins moving from one address to another, signed by the sender's key.
Confirmation — Each new page added on top of the one containing your transaction. Six confirmations ≈ carved in stone.
Transaction fee — What you pay miners for space on the page. Based on data size, not amount — $10 and $1 billion can cost the same to send.
Mempool — The waiting room: transactions broadcast but not yet included in a block. Fees decide who boards first.
UTXO — How the notebook actually tracks coins — as discrete chunks, like specific bills in your pocket rather than one account balance.
Lightning Network — Bitcoin's fast lane: instant, near-free payments that settle back to the main notebook. The bar tab.
Channel — A Lightning bar tab between two parties — open once, transact unlimited times, settle once.
Zap — Slang for a small Lightning payment, often a tip of a few sats.
On-chain / off-chain — On-chain: written directly in the notebook (slow, final). Off-chain: on a layer like Lightning (instant, settles later).
Double-spend — Trying to spend the same coin twice — the fraud Bitcoin was invented to make impossible without a bank.
Mining & the machine
Mining — The lottery that decides who writes the next page. Machines burn energy making guesses; the winner adds the block and collects the prize. Full story.
Miner — A machine (or the business running it) playing that lottery. Not a person with a pickaxe.
Proof of work — The rule that lottery tickets cost real energy. You can fake a vote; you can't fake work.
Hash — The output of a one-way math function — a digital fingerprint. Mining is guessing until you find a hash below a target.
Hashrate — The network's total guessing speed. Higher hashrate = a thicker security wall.
SHA-256 — The specific fingerprint function Bitcoin uses. Battle-tested, used across the internet's security systems.
Block reward — The prize for winning a block: newly created bitcoin plus that block's fees. Currently 3.125 BTC.
Halving — Every four years the block reward cuts in half — 50, 25, 12.5... down to zero around 2140. How the 21M cap gets enforced.
Difficulty adjustment — Every two weeks the network re-tunes the lottery's difficulty so blocks keep arriving every ~10 minutes, no matter how many miners join or quit.
ASIC — A machine built to do exactly one thing: mine bitcoin. Your laptop stopped being competitive around 2013.
51% attack — Controlling most of the mining power. Could briefly disrupt new transactions; could not steal coins or change the 21M cap. FUD page.
Node — A computer keeping a full copy of the notebook and checking every rule. Nodes, not miners, enforce what counts as valid bitcoin. Run one.
Consensus — Thousands of independent computers agreeing on one version of the notebook by following identical rules.
Fork — A change to the rules. Soft fork: backward-compatible upgrade. Hard fork: a split creating a separate network (and usually a new coin).
Culture & slang
HODL — Holding through the chaos instead of trading. Born from a 2013 forum typo of 'hold'; now a philosophy.