Re: Impact driver or impact wrench?
An air impact wrench uses a "hammer" and an "anvil" to create torque. A puff of compressed air throws the hammer forward and on the front of the hammer is a crown of slanted faces. The back of the anvil also has a crown of slanted faces and when the hammer hits them, it twists the anvil to the side. That's the "impact". Different units are rated for different maximal torque based on the angles on the hammer and anvil and on the force with which the hammer hits.
A manual impact wrench uses a hammer blow onto the back of the unit to accomplish the same torsional spike force by way of the same mechanism.
I've mostly heard people use the terms "impact wrench" and "impact driver" interchangeably, but that doesn't prove a thing. There could very well be a defined difference, but I haven't come across it.
An air ratchet uses a rotary mechanism powered by the compressed air and has much less torque, but it does a fantastic job of driving the many many full turns that it takes to put a connector like a bolt into it's place. Final torque specs are achieved using a torque wrench.