Hi bro. Upto my knowledge, squirel cage is actually the type of winding system in the corresponding motor. The winding is done on either stator, rotor or both and it is dependent on the design of the stator and the rotor. The shape of the stator, rotor or both is like a squirel cage. Iam sending a simple image of squirel cage rotor. Windings are done on the cylindrical bars between the rings. See wiki for better info.