In a foreign exchange market, a quote currency is the second currency in a currency pair. It is used to value or price the base currency, which is the first currency in the pair.
For example, in the currency pair EUR/USD (Euro to US Dollar), the quote currency is USD. This means that the pair indicates how many US dollars (quote currency) are needed to purchase one Euro (base currency).
The value or price of the base currency is always quoted in terms of the quote currency. This allows traders to easily compare the value of different currencies relative to each other, facilitating international trade and investment.
So when you see a quote like EUR/USD = 1.15, it means you need 1.15 USD to buy 1 EUR. The quote currency here, the USD, is the currency against which the value of the EUR (the base currency) is being determined.