Double insulation

Not all electrical appliances have earth wires installed.(Those appliances that has two pins only)
These appliances are double insulated. These insulation protects people from being electrocuted when there is a fault in the live wire. This is because the wire only touches the metal casing but the casing is insulated and wee cannot directly touch the casing, so we won't get electrocuted. Another reason why is because the insulation is an insulator of electricity, so it doesn't conduct electricity and therefore, we are protected from being electrocuted