A screwdriver is a type of simple machine. It can be either a lever or as a wheel and axle, depending on how it is used.
When a screwdriver is turning a screw, it is working as wheel and axle, using the rotation created by the handle to turn the screw quickly. In this example, the handle of the screwdriver is the wheel, while the shaft of the screwdriver is the axle.
When a screwdriver is used to pry up something, such as the lid of a paint can, it is being used as a lever. Usually, flat-head screwdrivers are used for this purpose.