Grounding is an essential part of Electrical Safety as it prevents dangerous electrical charges from building up. Any time electricity is used, it transfers a charge. Sometimes, electrical charges build up in metal components. If you were to touch a charged component, the electricity would flow through you into the ground, causing electrical burns or death. In order to prevent this from happening, electrical grounding is used, by connecting potentially charged components to large metal objects or the ground, thus removing any charge.
In AC Wall Plugs, the third prong (the one at the bottom) is connected to the house’s electrical ground, and is how common household electronics do grounding.
For Antennas, it is especially important to ground Antennas, because it reduces charge in the antenna, reducing noise and preventing lightning damage to radio equipment. Radios and Antennas are grounded using a Ground Rod driven into the ground. In addition, many HAMs buy Lightning Arrestors, which stops lightning before it approaches the radio by breaking a glass tube in case of high voltage.