Fuel injection is a system used to introduce fuel into an internal combustion engine. It involves the spraying of fuel directly into the cylinders under high pressure, as opposed to carburetion, where air and fuel are mixed together before entering the engine. The purpose of fuel injection is to provide precise control over the amount of fuel delivered to the engine, which can improve performance, efficiency, and emissions. It also eliminates the need for a mechanically complex system like a carburetor, making it more reliable and easier to maintain.