Polishing is to remove surface contminant that can not be remove with washing or even claybar. Usually tarnish area and lack of shine is due to contaminant stuck there..
Waxing is adding a layer of protection and shine. Usually the last step.
Ingeneral, the grooming steps are,
1. washing,
2. polish,
3. Wax.
Some people can be kiasu and add a sealant just before waxing for double proctection. Sometime can claybar just during washing with soap as the lubricant to remove gritty contaminant that is stuck.
