Their names are likely on that piece of plastic sitting in your wallet right now -- Visa, MasterCard, Discover, and American Express. No matter which one you have (or even if you have them all!), these companies have impacted the spending habits of people worldwide. Not all payment companies are created equally though. Each follows one of two business models that have come to set the basis for the payments industry. Understanding which business model is used is necessary for understanding any company in this space. Check out this slideshow to see just how these companies make their money by helping us spend ours.