Micro-maring is one of several names for microscopic scratches which can show up on highly polished surfaces as imperfections in the finish. Seen in the right light, they can appear as slight as a smudge or smear. They care caused by very fine scratches which would normally be invisible to the naked eye, but because there are hundreds or even thousands of them running parallel, collectively they reflect light when seen from certain angles. This is sometimes referred to colloquially as a hologram.
Usually these are scratches left by machine polishers, but on very soft paint could even be caused by a polishing cloth or drying towel.