A two-stroke engine is a type of internal combustion engine that completes a power cycle in just two strokes of the piston, or one crankshaft revolution. This design allows for a simpler and lighter engine compared to a four-stroke engine, making it popular in applications like motorcycles, chainsaws, and lawn equipment. In a two-stroke engine, the intake and exhaust processes occur simultaneously, which means it can produce power with every rotation of the crankshaft. This results in higher power output for a given engine size, but it can also lead to less fuel efficiency and higher emissions due to incomplete combustion.