The document discusses renewable and non-renewable energy sources. It defines energy and explains that it exists in all living and non-living things. Renewable energy sources like sun, wind and rain can be replenished, while non-renewable sources like coal, oil and gas are finite. The main advantages of renewable energy are wide availability, lower costs and less pollution, but their supply can be unreliable. Non-renewable sources are concentrated and reliable, but are highly polluting and will eventually be depleted.