A substance which can be used to carry or conduct electric charge from one place to the other is called a conductor.
Silver is one of the best conductors. Other examples of conductor are copper, iron, aluminum, mercury; coal etc. earth is a good conductor. Human body also a good conductor of electricity. The liquid conductors include, salt solutions, acids, alkalis etc.
In the metallic conductor, there are a large number of free electrons which act as carriers of charge. Infect, in a metal, the outer electrons part away from their atoms and are free to roam about in the body of metal, but they cannot leave the metal under normal circumstances. The free electrons from a kind of electron gas, they collide with one another; and also with the iron; and move randomly in the different direction.
The bound charges in the conductor as they cannot move.
The insulators are the materials which cannot conduct electricity. Ex: They are poor conductor of electricity. Common examples of insulators are glass, rubber, plastic, ebonite, mica, wax, paper, wood etc.
Insulators are also called dielectrics. Obviously, dielectrics cannot conduct electricity. However, when an external electric field is applied, induced charges appear on the surface of the dielectrics. Hence we may define dielectrics as the insulating materials which transmit electric effect without conducting.
When a charged body is brought in contact with the earth, all the excess charged on the body disappears by causing a momentary current to pass to the ground through our body. This process of sharing charges with the earth is called grounding or earthing.