Dual-fuel refers to a system or engine that can operate using two different types of fuel. This technology is commonly used in vehicles and power plants, allowing them to switch between fuels like natural gas and diesel or gasoline and ethanol. The ability to use multiple fuels can enhance efficiency and reduce emissions, making it a more environmentally friendly option. In a dual-fuel engine, the primary fuel is typically supplemented by a secondary fuel, which can help improve performance and reduce costs. This flexibility allows operators to choose the most economical or available fuel at any given time, contributing to energy security and sustainability.