Used in construction, Sheetrock and dry rock is the same thing. Sheetrock is a construction material, and it is a trading name. Drywall is a method used in construction. In other words, Sheetrock is a trademark of drywall, and it is registered with the United States Patent. Sheetrock is one of the reasons drywall because so popular.
This occurred after the company Gypsum, in the United States, introduced board panels made by Sheetrock. All sheetrocks can be referred to as drywall, but not all drywalls are sheetrocks. This because there are several names associated with drywall, which include wallboards, plasterboards, and gypsum.