Drywall, Sheetrock, Gypsum Board. Different names. Same material.
It's basically what most interior walls in residential and office building have been made of It began replacing plaster walls in the late 1950's. Plaster walls were very labor intensive to create.
Gypsum board which it is aptly called, is made of gypsum. This raw material is inexpensive to mine. The cost is much lower than plaster, because it can be efficiently mass produced in the factory.
While the labor to install drywall is much less than that of plaster, it still does require much labor to install the heavy sheets over the carpentry framework of a house. Furthermore, the next steps of "mudding" which is the covering of the seams between panels does time time and skill to get it smooth and level. If the carpentry underneath is not leveled out, the drywall will not be straight and flat.
Unfortunately, gypsum board is not particularly hard or strong, so it you bang into your walls with a hard heavy object, you will likely gouge or dent your wall. If you have teenage boys(sorry guys) you probably have seen an occasional hole or two in your walls.
We will expertly fix gouges, dents, AND holes in your walls (drywall, sheetrock or gypsum).
You've seen repair that are less than perfect (some are really bad)