The basic difference between rotational and translational motion is that, if you consider the trajectories of the particles of the body, in translational motion, all of them move in paths parallel to each other and the com(centre of mass). In rotation, the trajectories of the particles will be complex (since they involve both, translation& rotation abt COM )

 

The difference becomes clear if you consider the example of a wheel(rotation) and a cuboidal box(translational) 

 

You need to take account of both, translation and rotation, while solving a problem on rotation.