When trading, the term "long" is used to describe a position that generates profit if the market price of an asset increases. This is commonly referred to as "going long" or "taking a long position". In the forex market, going long means buying the base currency and selling the quote currency of a currency pair. For example, going long on EUR/USD involves buying euros and selling U.S. dollars.
Going long is the opposite of going short or "shorting", which refers to taking a position that generates profit if the market price of an asset decreases.
It's important to note that taking a long position doesn't always involve buying an asset. Derivatives allow traders to take a long position on a market without actually purchasing the underlying asset.