Basics
How the thing itself works.
Blockchain
A shared record of transactions, kept in blocks that each point to the one before, copied across thousands of computers so nobody can quietly change history.
Block
A batch of transactions added to the chain at once, sealed with the fingerprint (hash) of the block before it.
Bitcoin (BTC)
The first cryptocurrency (2009): a fixed supply of 21 million coins, secured by mining.
Altcoin
Any cryptocurrency other than Bitcoin.
Node
A computer that keeps a copy of the blockchain and checks new blocks against the rules.
Hash
A fixed-length fingerprint of any data. Change one letter of the input and the hash changes completely.
Mempool
The waiting room for transactions that have been sent but not yet put into a block. Higher fees get picked first.
Mining
Racing to find a number that gives a block a valid hash. The winner adds the block and earns new coins plus fees.
Proof of work
Security by spent energy: rewriting history would mean redoing all the mining since — faster than everyone else.
Proof of stake
Security by locked-up value: validators put coins at risk instead of burning electricity, and lose them if they cheat.
Confirmation
Each block added after the one holding your transaction. Six confirmations is the usual 'final' for Bitcoin.
Halving
Every 210,000 blocks (about four years) Bitcoin's new-coin reward is cut in half. Often linked to its four-year cycle.
Layer 2
A network built on top of a blockchain to make transactions faster and cheaper, settling back to the main chain.
Gas / fee
What you pay the network to process a transaction. It rises when the network is busy.
Markets
Prices, cycles and the words traders use.
Market cap
Price × coins in circulation. A rough size, not money that could actually be withdrawn.
FDV
Fully diluted value: price × every coin that will ever exist. A big gap to market cap means many coins still to unlock.
Liquidity
How easily you can buy or sell without moving the price. Thin liquidity means one big order can swing it.
Volatility
How violently a price moves. Crypto's is many times higher than stocks'.
Bull market
A long period of rising prices.
Bear market
A long period of falling prices — in crypto, often 75–85% from the top.
Altseason
A stretch late in a bull market when smaller coins rise faster than Bitcoin.
Whale
A wallet holding enough to move the market on its own.
DCA
Dollar-cost averaging: buying a fixed amount on a schedule instead of all at once.
HODL
Holding through the ups and downs instead of trading. Born from a typo of 'hold' in 2013.
FOMO
Fear of missing out — the feeling that pushes people to buy near the top.
FUD
Fear, uncertainty and doubt — bad news (true or not) that pushes people to sell.
Support & resistance
Price levels where buying or selling has repeatedly stopped a move.
Timeframe
How much time each candle on a chart covers — an hour, a day, a week. The trend can differ between them.
DeFi & tokens
Apps and tokens built on top of blockchains.
Token
A coin issued on top of another blockchain (for example an ERC-20 on Ethereum), rather than on its own chain.
Stablecoin
A token meant to stay worth one dollar (or euro). The good ones are backed by cash and bonds; algorithmic ones have failed.
Smart contract
A program that lives on a blockchain and runs exactly as written — including its bugs.
DeFi
Decentralised finance: lending, trading and earning through smart contracts instead of banks.
DEX
A decentralised exchange: you trade from your own wallet against a pool of tokens, with no company holding your funds.
Staking
Locking coins to help secure a proof-of-stake network, in return for a reward — and the risk of losing some.
Yield
The return on coins you lend or stake. Real yield always comes with real risk.
NFT
A one-of-a-kind token, often pointing at art or a collectible. Owning the token doesn't always mean owning the rights.
Airdrop
Free tokens sent to wallets — sometimes a real reward, often bait for a scam.
Token unlock
When locked tokens held by teams or investors become sellable. Big unlocks can push the price down.
Safety
Keys, wallets, and the ways people lose money.
Wallet
Software or a device that holds the keys to your coins. The coins themselves stay on the blockchain.
Private key
The secret number that can move your coins. Anyone who has it owns them.
Seed phrase
12 or 24 words that can rebuild your private keys. Write it down offline; never type it into a website.
Public address
Where people send you crypto. Safe to share, like an account number.
Hot wallet
A wallet app on an internet-connected phone or computer. Convenient, and more exposed.
Cold wallet
A hardware device that keeps keys offline and signs inside itself. Best for savings.
Custody
Who holds the keys. On an exchange, they do; in your own wallet, you do. 'Not your keys, not your coins.'
Rug pull
A project's team drains the liquidity or dumps its tokens, leaving buyers with nothing.
Phishing
A fake site, email or 'support' message built to steal your seed phrase or get you to sign something.
Token approval
Permission you give a smart contract to move your tokens. Old or malicious approvals can drain a wallet — revoke them.
DYOR
Do your own research — useful only if you know what to check.
Questions people ask
What does HODL mean?
Holding crypto through ups and downs instead of trading it. It started as a typo of 'hold' in a 2013 forum post.
What is FDV in crypto?
Fully diluted value: the price multiplied by every coin that will ever exist. A large gap to market cap means many coins are still to be unlocked.
What is the mempool?
The waiting room for transactions that have been broadcast but not yet included in a block. Miners usually pick the highest-fee transactions first.
What is a stablecoin?
A token designed to hold a steady value, usually one US dollar. The safer ones are backed by cash and short-term bonds.