What does these do to help the appearance of a car? I'm thinking it removes gunk?

 

Yeah sort of, gunk in the form of road debris, enviro fallout, and basically anything that prevents yours cars finish from feeling as a smooth as glass.

 

clay can scratch you finish so use some sort of lubricant like quick detailer. it removes wax, debris, and even overspray if its fresh enough.

after you clay your rig, remember there is not a single thing protecting the paint since all the sealants/waxes you had on there are removed now.