Retouching the skin and face is a meticulous process. The result is usually stunning. In today's easy access to Apps and Filters, the typical skin smoothing results in a horrible plastic/unnatural look. The look ends up being 100 times worse than the natural look. The resulting look is a doll like plastic look with absolutely no detail visible.
Professional skin smoothing and retouching will keep the details of the skin and yet smooth the skin. The natural tone of the skin should also be intact. Here is an example of skin retouching where I think the texture of the skin is still intact yet the skin is now smooth where it needs to be. Maybe someday I will post what a skin retouching isn't with what it is.
I am by no way saying I am the best in skin retouching, not at all. It is just that it is much better than the plasticky look that we are so used to by using those apps in social media.