The photon is the force-carrying particle of the electromagnetic interaction.
In quantum field theory, electromagnetic forces are described as interactions involving photons. Photons have zero rest mass, travel at the speed of light in vacuum, and carry energy and momentum. They have no electric charge, even though they mediate interactions between electrically charged particles.
Visible light is electromagnetic radiation made of photons, as are radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. These forms differ mainly in frequency, wavelength, and photon energy. Higher-frequency photons carry more energy according to the relation E = hf.
The photon concept was central to Albert Einstein’s 1905 explanation of the photoelectric effect. The photon is different from a gluon, which mediates the strong interaction, and from a neutrino, which is a matter particle rather than an electromagnetic force carrier.