Renewable vs. non-renewable energy

Renewable energy sources (solar, wind, hydropower, geothermal, biomass) draw on naturally replenishing flows that won't run out on a human timescale. Non-renewable sources (coal, oil, natural gas, and the uranium used in nuclear power) exist in finite, geologically formed quantities that are depleted as they're used. This distinction is about the resource's replenishment, not directly about emissions, though the two often correlate in energy policy discussions.