Compressed natural gas (CNG) is a type of fuel that is made by compressing natural gas, which primarily consists of methane. This process reduces the gas's volume, making it easier to store and transport. CNG is often used as an alternative to gasoline or diesel in vehicles, as it burns cleaner and produces fewer emissions, contributing to improved air quality. CNG is stored in high-pressure tanks and can be used in specially designed vehicles or converted engines. It is considered a more environmentally friendly option compared to traditional fossil fuels, and its use is growing in various sectors, including public transportation and commercial fleets.