Base currency means the currency in which your account is denominated. In other words, it is the currency you use to trade.
The available base currencies are; AUD, CAD, CHF, EUR, GBP, HKD, JPY, NZD, PLN, SGD, USD.
How do I open a live trading account?
How long does it take to open a trading account?
What is the main difference between Standard and Pro accounts?