Wax is acts a 'sealant' as it forms a barriers on the outside of your car so it seals the paint work in from the elements. But wax and sealants work in different way.
Wax is basically like rubbing a candle all over your car to get a thin layer all over your car so there is a barrier between your paint and the wind/rain.
Sealant 'bonds' to the paint work and has more to do with the chemical composition of the sealant, which then repels dirt. compared to WAX which is basically just wax, ie not many chemicals.
I think that is correct, best way I can put it for ya

And YES you can apply both a sealant and a wax, in which case you would apply the sealant then the wax to give your self uber protecion. However really only 1 is required when coming to the last stage protection LSP of your car.