What is a razor line that they do at barber shops? Curious?

I was wondering what a razor line is that they do at the barber shop? My friend was talking about this barber that he goes to can cut fades really well and that he does something called a razor line. What is that?What is a razor line that they do at barber shops? Curious?
A regular tapered haircut has the edge at the neckline tapered to the skin and usually has an outline shaved edge around the ear arches. Nothing is done to the edge at the forehead because the hair naturally tapers to very fine hair around the forehead. A ';bald fade'; is nothing more than a very short taper cut that has a very elongated edge around the ear arches tapered to the skin as at the nape. A line up is a shaved edge around the forehead. This artificial edge around the forehead usually looks artificial when cut and does not look good a few days later when it turns to stubble.What is a razor line that they do at barber shops? Curious?
its when they line up you forehead, sideburns and back of neck with a razor blade instead of a the clippers

gloss