this is from the online encyclopedia britanica.
"Photon - Minute energy packet of electromagnetic radiation. In 1900 M. Planck found that heat radiation is emitted and absorbed in distinct units,
which he called quanta. In 1905 A. Einstein explained the photoelectric effect, proposing the existence of discrete energy packets in light. The term
photon came into use for these packets in 1926. The energies of photons range from high-energy gamma rays and X rays to low-energy infrared and radio
waves, though all travel at the same speed, the speed of light. Photons have no electric charge or rest mass and are the carriers of the
Hope this sheds some light for you.