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 can lead to higher power output for the same engine size. However, this design often results in less fuel efficiency and higher emissions due to incomplete combustion and the mixing of oil with fuel for lubrication.