Two currencies change hands at today's rate, settled almost immediately. Every other FX trade in this course is a variation on this one.
An FX spot trade is a straight swap of one currency for another at today's exchange rate, settled almost immediately — typically two business days later, known as "T+2".
No forward-looking commitment, no notional trick — the full amounts on both sides actually move.
A US company paying a European supplier needs euros, so it sells dollars and buys euros spot. A trader who thinks the euro is about to strengthen buys it outright.
It's the simplest way to convert value from one currency into another, right now.
It's the largest, most liquid market in the world by a wide margin — importers and exporters converting real trade flows, travellers changing cash, and trading desks moving trillions of dollars a day.
Almost every other FX product in this course — forwards, swaps — is built from this trade plus a date.