If I was to give you a nice crisp £10 note (or the equivalent in your local currency) no strings attached what would you do with it?
Alternatively, if I was to give you £10 but instead stipulated that you had to return the £10 back to me within 48 hours, what would you do with it then?
You can use the money for absolutely any purpose and if you make a profit, you get to keep the difference.
How big a return could you make in two days?