My notes say
Radiation emitted from any source moves discontinuously in form of small packets of energy. Each packet is called quantum.
Does this mean that when light travels, it is actually a particle jiggling up and down (and moving forward simultaneously, of course) creating a path that looks like a wave and is that why we call light to be travelling "like a wave"?
Possible duplicate of What is Planck's quantum theory of radiation?
But no satisfactory answer there, so asking again..