It actually Foreign Exchange Currency. You'll buy or sell currency base on their price. For Example you buy Eur/USD mean you long on that currency and if the EURUSD going up mean you'll get profit from that if going down you'll loss your money. More info you can check this site
Forex Education, Forex Training, Currency Trading, Beginner's Guide to Forex Trading, Learn Forex, Foreign Exchange - BabyPips.com