A ground wire is a safety feature in your house. It is an electrical wire that is connected to a metal rod that is buried in the ground. This metal rod is connected to the Earth, and the ground wire is connected to the metal rod.
The ground wire is connected to all the electrical outlets in your house. It helps keep the electricity in the outlets safe by providing a way for the electricity to go if it becomes too strong. Instead of the electricity staying in your outlets and hurting you, it flows safely into the ground away from you.