I've seen the reference on here before concerning "overseeding" and am not exactly sure what it means. Is this just what it says, that you seed over existing grass or sod, and is it used to get a thicker sod? Someone get me going on the right track concerning this process. Assuming my thoughts are right, how successful is this procedure. I have some yards that the grass needs some help choking out the undesirables, and am wondering if this may help. These aren't bald spots, just not all good grass.