What is the grounded terminal of a receptacle identified by?

I believe you are asking for a description of the electrical "Earth" or "Ground" symbol (?) It is drawn as 3 horizontal lines (one above another), of decreasing length toward the top. The bottom line is intersected at its centre by a short vertical line that heads downward. The symbol is usually drawn inside a circle. An "Earth" or "Ground" wire is normally identified by Yellow and Green striped sheath or tape.