To give you an analogy, the same difference between an Airline and its flight number.
Foreign Exchange refers to a currency type. For example US Dollars, or Philippines Peso, Kenyan Shillings, etc.
Foreign Exchange rate refers to the the exchange rate between two currencies.
If I hand over to you 1 unit of my currency, how many units ofyour currency will I get? That is what the foreign-exchange rate tells us.