There are two more equations to remember:
Long means buy
If you want to buy a currency (meaning that you want to BUY the base currency and SELL the quote currency) at one price and sell it later on at a higher price, then you are in trade's talk taking a "long position" or "going long".
Short means sell
If you want to sell a currency (meaning that you want to SELL the base currency and BUY the quote currency) in order to buy the base currency back at a lower price as soon as the base currency decreases in value, then you are taking a "short position" or "going short" .