 Well, the deeper you go into the Earth's crust, the hotter it gets. And if you drill down deep enough, you can access temperatures that are hot enough to generate steam and spin a turbine, which can be used to generate electricity just like we might in, say, a coal-fired power plant or natural gas plant, except this energy is renewable and clean and doesn't produce any air pollution or CO2 emissions. What's the advantage of enhanced geothermal over, say, wind or solar power?