It's basically selling debt.
Or at least something like debt. It is a fixed payment, quasi interest barring debt (actually not interest but fixed cost).
Neither of these explain it to me like I am five years old. Could someone please be very explicit about it? I'm sorry that I don't understand; I am just so naive about anything related to money.
What would it mean if I were to click one of the buttons that says BUY on the Open Sell Orders? What would happen?
Quite honestly if you are five years old, you shouldn't be using BTCJam. It is basically a way to get a loan from your peers, or a way to offer a loan to your peers.