Wax is a product that you would go over the car after it has been polished. Say you used the likes of Lime Prime from Dodo Juice to polish your car, It contains some fillers plus other bits so over a few weeks these will be washed/were off leaving your paint open to elements making it shine less and get covered in fall out. If you where to wax over the top after you have polished your adding a thin lair of protection to the paint meaning the shine will last longer and the paint is protected.
You can also use a sealant like (Supernatural Hybrid Paste Sealant) instead of a wax these tend to be man made and will offer a longer period of protection but have a little bit less of a shine.
And just to confuse you even more you can add a glaze like Poorboys Black Hole after you polish this will add to the shine and fill in light swirls but you must still wax over it.
It wont dull your paint but remember a polish contains micro abrasives so doing it all the time wont be good for your paint plus there is always the risks of adding more swirls.
