Crypto to fiat currency trading refers to the use of fiat currency to buy and sell digital currency, with a fiat currency as the unit of valuation to buy digital currency. The trading rules are to complete matching transactions in accordance with price priority and time priority, and directly realize transactions between digital currencies.

For example, Bitcoin (BTC), Litecoin (LTC) and other digital currencies are priced with the US dollar (USD). When Bitcoin is priced with the US dollar, a transaction currency pair of BTC/USD is formed (when one currency is priced with another currency, a transaction currency pair is formed). The price of the pair represents how many units of USD you have to pay to buy 1 unit of BTC, or how many units of USD you get for selling 1 unit of BTC.