A short upper lip is said to be one of the factors we humans subconsciously use in determining facial beauty. It is more common in women than in men. There's something about pearly white teeth, perfectly aligned, that the human animal finds attractive. It probably has something to do with perceived health and procreation, you know, survival of the fittest.
The procedure involves making an incision under the nose, in an area that easily hides scarring, and removing a section of skin underneath that. In the process a surgeon can try to expand the upper lip or curl it up to create a more feminine appearance.
Immediately after I had mine, my lips would not close naturally, as they had before. That was almost four years ago. Today that is no longer true. For me, the procedure was pretty much no big deal, but at the time I was in so much pain from FFS if there was any pain from the lip lift I wouldn't have known it. It healed quickly though. And you have to look very closely to see the scar.