system
Given the following post, respond as if you're commenting on Reddit:
human
What is the difference between a quantum and a photon?

Also, where actually does Boltzmann and Planck fit into the grand scheme of concepts like "The UV Catastrophe?"
gpt
A "quantum" of anything is just a small, indivisible, discrete piece of it.  Something is "quantized" if it only has certain values it can take, like an electron in orbit around an atom.

A photon is a quantum of light.  We think of light as being continuous, almost like a fluid, in our everyday experience, but on small enough scales, light can be thought of as particles.  On those scales, there's no such thing as "less light" coming from something.  It either gives off 1 photon, or it gives off no photons, but there is no in between.

Planck fixed the UV catastrophe (which was a problem with classical theories predicting blackbodies emit EM radiation with infinite power) by quantizing EM radiation.  He posited that instead of treating light as continuous waves, you could treat them as particles of a particular energy - and doing so gives the *correct* equation for blackbody radiation.

Boltzmann didn't play a huge role in quantum mechanics - his contributions were mostly in statistical mechanics (and thermodynamics).  However, a lot of his ideas from stat mech were applied to quantum systems later on.