The main difference between a three-pronged plug and a two-pronged plug is the grounding wire. A three-pronged plug has a grounding wire, an extra safety feature designed to protect you from electrical shock. A two-pronged plug does not have a grounding wire and is used for appliances that do not require groundings, such as lamps, small appliances, and electronic devices with plastic casings. Overall, using three-pronged plugs is safer than two-pronged plugs, as they provide an extra layer of protection against electrical shock. Using the correct plug for each appliance or device is important to ensure safety and prevent electrical hazards.