Protect Paint with Wax
You car had a new clear coat when it left the factory, but that coat wears off over time and leaves the paint to fend for itself against the elements. That's where wax comes in. Wax is sacrificial and will wear off over the course of a few months, but in that time it will absorb stains and small scratches before those hazards make it to the paint. We're told older folks prefer paste wax, while younger ones like liquids. The choice is simply personal preference—both products do the job equally well. Finally, the pro detailers usually use two coats of wax; the purpose of the second coat is to cover areas that the first might have missed. Just don't waste your time trying to apply additional coats for added protection. They don't adhere and will be wiped off with buffing.