An RF (Radio Frequency) Antenna is a device designed to transmit or receive radio frequency signals wirelessly. It converts electrical signals into electromagnetic waves, which can then be transmitted through space or received from the air. It's used in various applications, such as broadcasting, mobile communication, satellite communication, radar, and wireless networking.

It's come in different types, shapes, and sizes, depending on their application and frequency range. Some of the commonly used antenna types include dipole, monopole, patch, helical, Yagi, and parabolic antennas. The choice of antenna type depends on factors such as frequency range, radiation pattern, gain, polarization, and impedance.