Polishing:-
Polishing means removing a small layer of your clear coat to reveal the new, shiny layer(This is the simplest defintion of Polishing).There is a hell lot of diffference between Polishing and Waxing.So,for a frequent usage,you need a wax, and if you are able to maintain your car's paint with frequent waxing, after the detailing session which includes polishing, you need not to polish your car.Factory paint is already very thin and it is not advisable to polish it every now and then.
[I]Polishing removes paint imperfections like swirls,spiderwebs,orange peel etc and reveal a shiny mirror like surface.This step shouldn't be repeated again and again.Once in two or three years.
[/I][U]Waxing:-[/U]
After you are done polishing the whole car,you may now to proceed to the next step i-e sealing your paint with a good wax.Two types of waxes are Carnuba Wax and Synthetic Wax.
Carnuba Wax:- Carnuba Wax is found in the leaves of palm trees,which protects its leaves from the dazzling heat of sunlight i-e UV Rays.Same is the case when it is applied to car's paint, it protects it from UV Rays.Carnuba Wax doesn't last long and you need to apply it probably afer a week.Infact, in our environment we need to apply wax, whether it is synthetic or Carnuba.
Synthetic Wax/Paint Sealant:-Synthetic wax contains man made substances and last longer.That is why another professional name for a synthetic wax is paint sealant.People confuses the paint sealant with something different.But infact, both are same things.If an ordinary person goes to an ordinary shop and ask him about Paint Sealant,the shopkeeper will become blank about what the consumer is asking.So, for an entusiast as the primary intender is a consumer, it is synthetic wax, while for a professional it is Paint Sealant.
The best example is Meguiar's TechNXT 2.0 and Meguiars Synthetic Sealant2.0(Both are same things)
Waxing can be done as often as you want to maintain the shine of your car.