This may be the next question you have...
Photons are easy because they are simply the particles that make up light.
They have no mass, and so they move at our universe speed limit of 670 million
miles per hour. Photons have different energies which means that they have
different frequencies. For instance, humans can't see infrared photons
because the frequency is too low, and we can't see ultraviolet light because
their frequency is too high. However, humans are smart enough to build
instruments that can see this light.