Alternative energy refers to energy sources that are different from traditional fossil fuels like coal, oil, and natural gas. These sources include solar energy, wind energy, hydropower, and geothermal energy. They are considered more sustainable and environmentally friendly because they produce little to no greenhouse gas emissions and can be replenished naturally. Using alternative energy can help reduce dependence on finite resources and combat climate change. For example, solar panels convert sunlight into electricity, while wind turbines harness wind power. By investing in these technologies, societies can work towards a cleaner and more sustainable energy future.