Fuels are substances that store energy, which can be released to perform work or produce heat. They are essential for various applications, including transportation, electricity generation, and heating. Common types of fuels include coal, natural gas, and oil, each with unique properties and uses. The combustion of fuels releases energy, but it also produces emissions that can impact the environment. As a result, there is a growing interest in alternative fuels, such as biofuels and hydrogen, which aim to reduce carbon footprints and promote sustainability in energy consumption.