What's your one-line summary of how forex works?

If you had one sentence to explain currency trading to a complete newcomer, what would it be? The best explanations are short, honest and free of hype.

Post yours. No long paragraphs — one or two sentences each, the kind of thing you'd say to a friend over coffee.

Then read everyone else's. The differences in emphasis say a lot about how each of us actually thinks about this market.