Typically an antenna consists of an arrangement of metallic conductors (or "elements") with an electrical connection (often through a transmission line) to the receiver or transmitter. A current forced through such a conductor by a radio transmitter will create an alternating magnetic field according to Ampère's law.
Or the alternating magnetic field due to a distant radio transmitter will induce a voltage at the antenna terminals, according to Faraday's law, which is connected to the input of a receiver. But it is only through antennas that those radio frequency electrical signals are converted to (and from) propagating radio waves.
Depending on the design of the antenna, radio waves can be sent toward and received from all directions ("omnidirectional"), whereas a directional or beam antenna is designed to operate in a particular direction. In the so-called far field, at a considerable distance away from the antenna, the oscillating magnetic field is coupled with a similarly oscillating electric field; together these define an electromagnetic wave which is capable of propagating great distances.
Light is one example of electromagnetic radiation, along with infrared and x-rays, while radio waves differ only in their much lower frequency (and much longer wavelength). Electronic circuits can operate at these lower frequencies, processing radio signals conducted through wires.