A working glossary for stablecoin payments and crypto cards. Terms are grouped by where you meet them.
Stablecoins & value transfer
Stablecoin — A cryptocurrency engineered to hold a steady price, usually $1, via reserves or collateral. See Stablecoins 101.
Peg — The target price a stablecoin tries to hold. “Holding the peg” means trading at ~$1.00.
Depeg — When a stablecoin trades meaningfully away from $1. Can be a brief liquidity wobble or the start of a collapse; context matters.
Attestation — A third-party report confirming an issuer’s reserves at a point in time. Weaker than a full audit; still the main transparency tool for fiat-backed coins.
Mint / Redeem — Creating stablecoins by depositing dollars with the issuer (minting), or returning coins for dollars (redeeming). Retail users usually trade on exchanges instead.
Networks & wallets
Network / Chain — The blockchain a token lives on. USDT exists on Ethereum, Tron, Solana and more; the same coin on different chains is not interchangeable without a bridge or exchange.
Gas — The fee paid to the network to process a transaction. On Ethereum it’s paid in ETH; on Tron, in TRX. You need a little of the native token to move any token.
Address — The destination string for a transfer (e.g. 0x… on Ethereum, T… on Tron). Transfers to a wrong or wrong-chain address are usually unrecoverable.
Self-custody vs custodial — Holding your own keys (self-custody) versus letting an exchange or card provider hold funds for you (custodial). Crypto card balances are custodial by definition.
Seed phrase — The 12–24 words that back up a self-custody wallet. Anyone with these words owns the funds; never type them into a website.
Moving between fiat and crypto
On-ramp / Off-ramp — A service that converts fiat money into crypto (on) or back (off): exchanges, card top-ups, P2P markets.
P2P trading — Buying stablecoins directly from another person via an escrowed marketplace. Common where card purchases of crypto are restricted; requires care with counterparty and receipt checks.
Spread — The gap between buy and sell prices. On-ramps often charge “0 fees” while earning inside the spread — compare the effective rate, not the fee line.
Cards & payment rails
BIN (Bank Identification Number) — The first 6–8 digits of a card number, identifying the issuing program. Merchants and fraud systems use it to classify your card.
MCC (Merchant Category Code) — A four-digit code classifying the merchant (groceries, gambling, money transfer…). Issuers approve or decline partly based on MCC, which is why some cards refuse specific purchase types.
3-D Secure (3DS) — The extra verification step on online payments (Visa Secure / Mastercard Identity Check), usually an in-app or SMS confirmation.
Authorization — The real-time approve/decline decision on a transaction, and the temporary hold it creates. Explained fully in how card authorization works.
Clearing & Settlement — The back-office stages after authorization where the final amount is confirmed and money actually moves between banks, typically T+1.
Chargeback — A card-network dispute process that can reverse a payment. A consumer protection with no equivalent in on-chain transfers — one reason cards remain useful.
Foreign transaction fee — The percentage an issuer adds when you pay in a currency other than your card’s base currency. Distinct from the network’s exchange rate itself.
Regulation
KYC / AML — “Know Your Customer” identity checks and “Anti-Money-Laundering” controls. Every reputable card provider requires identity verification; tier limits usually rise with verification level.
MiCA — The EU’s Markets in Crypto-Assets regulation, fully in force since the end of 2024, with strict rules for stablecoin issuance and e-money tokens.
GENIUS Act — The 2025 US federal law creating a licensing and reserve framework for payment stablecoin issuers. More in regulations.
Missing a term? This glossary grows with the wiki — new entries are added as the blog covers them.