Forex terms: Currency

Currency is the form of coinage that a country uses to trade.  England, for example uses the GBP or British Pound, whilst the USA uses the USD or US Dollar.  The currency price varies throughout the day for various different reasons, so if you buy a currency in the morning, by the time you sell it in the evening, it wont be worth the same amount as it was when you bought it.  These changes in the value of currencies against other currencies is what makes Forex trading possible.