Rotating your wheels can increase the longevity of the tyres, prolonging your next purchase and getting more bang for your buck! Depending on the drive of the vehicle, the tyres on the front and rear axles can have different wear levels, therefore rotating will yield even wear.

If you have directional/unidirectional tyres, you can only use a 'front-to-back' rotation unless you refit the tyres to the rims.  

If you have asymmetrical/symmetrical tyres, you can use a 'front-to-back' and 'side-to-side' rotation as per the below image.