Is a wheel and axle simple machine consisting of two wheels different sizes that rotate together?

Yes, a wheel and axle is a simple machine consisting of two wheels (or cylinders) of different sizes that rotate together. The larger wheel is the "wheel" and the smaller wheel is the "axle". A force applied to the larger wheel results in a greater force at the smaller axle, or vice versa, depending on which part of the machine the force is applied to.