Antenna gain refers to the ability of an antenna to focus energy in a specific direction compared to a standard reference antenna, usually an isotropic radiator. It is measured in decibels (dB) and indicates how well the antenna can transmit or receive signals. A higher gain means the antenna can send or receive signals over longer distances or with better clarity. The gain of an antenna is influenced by its design, size, and shape. For example, a parabolic dish antenna typically has a high gain due to its ability to concentrate signals, while a dipole antenna has lower gain. Understanding antenna gain is essential for optimizing communication systems.