If you don’t know much about Islamic finance, here’s a pretty good explanation in strategy+business. In short, Islamic finance is a financial system that does not “permit payment or collection of interest, nor transactions based on speculation or risk.” So how do you earn a return on your funds if you cannot earn interest? Have a read http://www.strategy-business.com/article/08217?pg=all
Incidentally, back when I worked for HSBC, I heard great stories from some folks who worked in the Middle East about how bankers would structure transactions. Sometimes they went something like this:
Banker: How about you give me your big pile of money and when I give it back to you in one year, I will give you a Mercedes S-Class?
Client: What colour?