It depends on what you're doing with the forex trading. If, as I'm guessing is the case with your brother, you trade with the hope/expectation that a rate will

It depends on what you're doing with the forex trading. If, as I'm guessing is the case with your brother, you trade with the hope/expectation that a rate will move towards you in the future and you'll profit from that rate move, then that's just common or garden gambling. But it's also used to buy or sell currency because you cash in that currency, hedge the forex component of an asset/liability, make a market etc. Different people have different use cases.