A curved shaft trimmer is one where the cutting head and blade are attached to the end of a curved boom. This type of trimmer is lighter and easier to maneuver than a straight shaft trimmer. The blades on a curved shaft trimmer are also less likely to come into contact with your legs or feet as you trim.
A straight shaft trimmer has a long, straight pole that extends from the cutting head to the motor. This type of trimmer is heavier and more difficult to maneuver than a curved shaft trimmer, but it provides more power and reach. The blades on a straight shaft trimmer can also be positioned closer to the ground for better cutting performance.