Why there are many oil prices

We talk a lot about the price of oil on this show, but there are actually dozens of types of oil. On today's program, we're learning about where they come from, what they're used for, and why the price of oil futures differs from oil's on-the-spot market price. And later, as energy gets more expensive, governments around the world are asking people to try to conserve energy. How much of an impact do those moves have?