2002 Hyundai Accent valve cover gasket

What you're describing is typically found on one end of the cylinder head right under the valve cover. It may be referred to as a "cam plug" because it is inline with the end of the camshaft. Often gasket sets will come with a few gaskets you don't use or have on your car. There can be a number of variations, and rather than make a lot of different sets that someone has to stock, they make a "one-size-fits-all" set that includes everything you might need, regardless of which variation of engine you have.