In the forex market, currencies are always quoted in pairs. The value of a currency is determined by comparing it to another currency.
The following are examples of currency pairs: USD/JPY, EUR/USD, USD/CAD, AUD/CAD...
In a currency pair, the first currency is called the "base currency", and the second is called "the quote or counter currency". For example, in the EURUSD currency pair, Euro is the base currency and USD is the quote currency.
The base currency is always equal to one monetary unit. If the EURUSD quote is equal to 1.3, this means that one Euro is equal to 1.3 Dollar.