Driver side rear tire and possible dc joint

I recently changed both rear brakes and rotors. After doing this during rest drive passenger side was making grinding noise. So after I jacked car up again I went to remove wheel and that is when I noticed that the wheel wiggled in and out.I think the problem stems from a part that is connected to the hub it is covered by a accordion looking rubber boot the whole assembly moves up and down which does not happen on other side piece also has part of anti lock brake system attached to it is this a cv joint I am worried cause I know it needs replacement but I am unsure what this part is. Could it be a axle shaft, cv joint joint, I am unsure could you please help me identify this part. THANK YOU