Forex is always traded in currency pairs – for example, GBP/USD (Pound v US dollar). You speculate on whether the price of one country's currency will rise or fall against the currency of another country, and take a position accordingly. Looking at the GBP/USD currency pair, the first currency (GBP) is called the 'base currency' and the second currency (USD) is known as the 'counter currency'.
When trading forex, you speculate on whether the price of the base currency will rise or fall against the counter currency. So in GBP/USD if you think GBP will rise against USD, you go long (buy) the currency pair. Alternatively, if you think GBP will fall against USD (or that USD will rise against GBP), you go short sell the currency pair.
Find out what are some of the most traded currency pairs in the forex market by reading our in-depth guide.