A four-stroke engine is a type of internal combustion engine that completes a power cycle in four distinct strokes of the piston. These strokes are known as intake, compression, power, and exhaust. During the intake stroke, the engine draws in a mixture of air and fuel. The compression stroke then compresses this mixture, making it more explosive. Next, the power stroke occurs when the compressed mixture is ignited, causing a small explosion that pushes the piston down. Finally, the exhaust stroke expels the burnt gases from the cylinder. This efficient process is commonly found in vehicles like cars and motorcycles, making them powerful and reliable.