The materials that don’t allow electrical charges pass through it easily are called insulators.
The ability of electrical energy to pass through materials is known as conduction. Materials such as glass, rubber, cloths and plastic are poor conductors of electricity. Though these materials are poor conductors of electricity that doesn’t mean they cannot pass electricity at all.
However, if they are attacked with thefull force of voltage they become conductors of electricity, some insulators can become conductors when they are wet.