What is the difference between a renewable and nonrenewable energy source?

Nonrenewable energy sources are those, like fossil fuels pumped or mined from beneath Earth's surface, that exist in a finite supply. In other words, once the oil, coal and natural gas deposits of the world are exhausted, that's it. There will be no more of those sources of energy (although, coal in particular is available in large quantities, its polluting qualities notwithstanding). Fossil fuels, of course, are called "fossil fuels" precisely because they are the physical remains of long-dead plants and animals, most dating back to prehistoric periods, even before the dinosaurs. They are nonrenewable because it took hundreds of millions of years for coal and oil to form, and because fossil fuels do exist in finite quantities.

Renewable energy sources, in contrast, are those that naturally replenish such as solar power. Solar power, as the name suggests, is derived from the enormous energy emitted from our nearest star, the Sun. Other forms of renewable energy are wind, water, and geothermal, which is derived from heat that emits directly from the subsurface layers of Earth. While water is considered a renewable form of energy, it probably should not be so categorized given the fragility of much of the planet's fresh water supplies. Water, as we know from vast natural formations like the Grand Canyon, wields enormous power, and is naturally renewable in the form of precipitation. However, its over-usage by modern industrial societies and its waste in inefficient agricultural practices in much of the less-developed world leads to the question of whether water power can be considered a viable form of renewable energy.