Cleaning (Level of Security)

Norton 360 does a good job of cleaning up unnecessary files caused by web surfing, working with files, etc., but I find nothing about actual levels of permanent removal (DOD, Gutmann, etc.).  Thus, doesn't the file actually still stay on the computer taking up space?  If so, what's the point of running file cleanup?  If there is permanent removal, what is the method?

Norton 360 does a good job of cleaning up unnecessary files caused by web surfing, working with files, etc., but I find nothing about actual levels of permanent removal (DOD, Gutmann, etc.).  Thus, doesn't the file actually still stay on the computer taking up space?  If so, what's the point of running file cleanup?  If there is permanent removal, what is the method?