The primary characteristic of renewable energy sources is their ability to regenerate naturally over time, providing a sustainable alternative to fossil fuels. Examples include solar, wind, hydroelectric, and geothermal energy, which harnesses natural processes to generate power. These sources produce minimal greenhouse gas emissions, contributing to a reduced environmental impact compared to fossil fuels. By relying on renewable energy, societies can enhance energy security, decrease dependence on finite resources, and support global efforts to mitigate climate change.