All currency is/was money but not all money is currency.
Currency is money which is authorised by law: UK Pounds, US Dollars, Thai Baht etc.
Money is anything that is used as a store of value and medium of exchange: All currency plus bitcoins, cigarettes in a prison, virtual money in an online game, gold, silver etc.
Now, there is also currency that is no longer money: Confederate States of America Dollars, Reichsmarks, coins minted by King John of England etc.
However, for our purposes, it's probably OK to consider them synonyms.