A photon is a unit of measurement for energy. It’s a fundamental particle.
It might be the quantum of the electromagnetic field including electromagnetic radiation such as light.In a vacuum, the photon has no rest mass and always flows at the speed of light.
A quantum is the smallest amount of any physical entity (physical attribute) engaged in an interaction (plural: quanta).
A photon, for example, is a single quantum of light that might be called a “light quantum” or a “light particle.”
Difference
A photon possesses both wave and particle qualities, but quantum does not.
Quantum can be compared to a unit of measurement, however a photon is not a unit of measurement of quantity
Final Answer:-
A quantum is the smallest packet of energy in any radiation, whereas a photon is the smallest packet of energy in light.