Paint correction is a term that is now commonly used by both professional car detailers and car cleaning enthusiasts worldwide to describe the process of restoring and rejuvenating the paintwork of a vehicle, mostly through the elimination of surface imperfections, that dull, oxidize, or haze the surface by reflecting light off in various directions, therefore detracting from a true and proper, clean, sharp, reflection. These imperfections include things like swirl marks & fine scratches, bird dropping etching & acid rain etching, hologramming & buffer trails, and random isolated deep scratches (or RIDS).
This is a before and after of paint correction on a car with heavy swirls and light scratches. This car was abused from automated washes all it's life, however we were able to restore the paint to near factory conditions. Aside from the swirl marks being removed, you can also notice a difference in the depth and gloss of the paint.