Earthing (grounding) gives stray electricity a safe path into the ground instead of through a person. If a fault makes an appliance's metal body live, a good earth connection carries that current away and lets the protective device trip — preventing a potentially fatal shock.
Every modern home should have proper earthing, and the earth wire (the third pin on a plug) should run to all socket circuits and metal-bodied appliances like geysers, washing machines and ACs. Earthing also helps protect equipment from voltage surges.
Earthing quality depends on both the installation and the conductor used. Have it tested by a licensed electrician, and use reliable house wiring for the earth conductor. It works alongside MCBs and safe cabling as part of a complete safety setup.