First published 11 February 2020 as a long A-to-Z dump. We rewrote it in August 2026, and expanded it in October 2026, into the terms that actually stop people. If a word is not here, you probably do not need it yet. For the six-step path, start at Learn.
Wallet
Software or hardware that holds keys, or a company account labelled “wallet”. The network holds the coins. Only keys (or the company’s promise) can move them. See how wallets actually work.
Seed phrase / recovery phrase
Usually 12 or 24 words that reconstruct the keys. Anyone who sees them can spend. Support will not ask for them. A screenshot is a backup for thieves. Write them once, store them offline, test a restore with a tiny amount.
Address
A public string you can share so someone can pay you. It is not secret. Sending to the right characters on the wrong network is still a loss. Copy, then check the first and last characters on the device screen.
Private key
The secret that can sign a spend. Seed phrases are a human-readable way to derive keys. If a site asks you to “import” or “validate” a phrase to claim something, it is not a wallet. It is a harvest.
Gas / network fee
Payment to whoever includes your transaction. On Ethereum it is called gas. Busy moments cost more. A failed transaction can still cost a fee. Cheap and fast is not the same as final and reversible.
Token
A balance inside a smart contract that your wallet knows how to display. ETH on Ethereum is native; USDT on Ethereum is a token. A pretty icon is not a certificate of authenticity. Copycat tickers exist.
Stablecoin
A token that aims to stay near a unit such as a US dollar. Some are company IOUs (you trust an issuer). Some are over-collateralised on-chain (you trust code, oracles, and liquidation). Pegs can break. “USD” in the name is branding.
Exchange
A company that matches buyers and sellers, or a pool of contracts that does something similar. Custodial exchanges can freeze accounts. Decentralised ones can still drain you via a bad approval. An order book is not a vault.
Market cap
Price multiplied by coins treated as circulating. A round number is a headline, not a law. Tiny unit prices on huge supplies are not discounts. Illiquid coins can print a market cap nobody could actually sell into.
On-chain / off-chain
On-chain means recorded on the public ledger. Off-chain means a company’s database, a receipt, or a promise. “I have bitcoin at an app” is often off-chain until you withdraw.
Confirmation
A transaction appearing in a block, then in the blocks that follow. Wallets show “sent” before the network has agreed. Exchanges wait for a number of confirmations because history can still reorganise for a moment.
Cold storage
Keys that are not sitting on an internet-connected daily driver. Still stealable if you photograph the backup. See the cold-storage guide.
Passphrase
An extra secret some wallets add on top of the 12 or 24 words. It opens a different, hidden set of keys. It is not the recovery phrase, and it is not the PIN that unlocks a device. Forget it and the coins behind it are gone even if you still have the words. If you never turned one on, you do not have one. A website that asks for “your passphrase” usually means the recovery phrase, and is phishing either way.
UTXO
An unspent transaction output: one note of bitcoin left over from an earlier payment. Bitcoin wallets spend notes and often send change back to you. Ethereum does not work this way; it keeps a running balance on an account. If a fee looks strangely high, you may be spending many small notes. See what is a Bitcoin wallet.
Mempool
The waiting room of transactions that have been broadcast and not yet written into a block. A low fee waits there. Waiting is not theft. A website that offers to “accelerate” a stuck transaction by asking for your recovery phrase is not accelerating anything.
Layer 2
A network that batches work and settles back to a base chain, usually Ethereum. Cheaper and related. Not the same notebook. The same-looking address on a layer 2 is a different balance. See the wrong network is still the wrong city.
Destination tag / memo
An extra field some networks and many exchanges require, so a shared deposit address can tell customers apart. XRP is the famous case. The address is the building. The tag is the flat number. Omit it and the coins can sit in a lobby. Copy it from the deposit screen, every time.
Slippage
How far a trade can move the price while it is happening, especially in a thin pool. A decentralised swap is trading against a pool, not a shopkeeper. A large slippage setting is permission for a worse price. It is not a fee discount. DeFi is software with rules you cannot call support about.
Liquidation
A loan or a leveraged contract being closed because the collateral no longer covers the venue’s minimum. On a perpetual, the exchange’s risk engine does it. In a lending protocol, a bot does it. It is the product working. It is not the blockchain taking a coin you hold outright. A perpetual is a contract with no expiry, not a bigger coin.
This page is a map of language, not a product list and not financial advice. When a headline uses one of these words as a command, read it again as a description.
