There are two broad categories of product used when 'polishing' cars: those that add a sacrificial barrier to your paintwork to protect it after polishing, and those that remove dead paintwork during the polishing process. Combination products do both at the same time. They typically contain a very light polish for removing oxidized paint, while also adding a synthetic wax as protection.
This can lead to some confusion as these products are seldom labelled as a combination product, instead being labelled either a wax, sealant or polish. The most famous example of this in the UK is AutoGlym's Super Resin Polish. It is a very good light chemical polish, it is also a very good wax.