im confused about baryons. they say that it is a particle (presumably like an electron or photon or other particle) but then they go on to say that its a gas, not a particle. very confusing.
A gas in this sense is really a very loose collection of light particles, mainly hydrogen/helium or just empty separate protons and neutrons. As opposed to heavier atoms that are the product of stellar fusion and form more solid matter.
If you think about this in terms of cosmology, the universe was originally a solid uniform blob of high energy particles. As it cooled, some of those particles grouped together to form stars and galaxies. However, there are parts in between galaxies that clumped together a bit but didn't really have enough mass to form anything. So it's really just made of tendrils of basic atomic building blocks.
Atoms are made up of protons, neutrons, and electrons. Between the 3 types of particles the mass of the protons and neutrons outweighs that of the electrons by about 3 orders of magnitude, almost all of the mass is in the nuclear particles. And those particles are baryons, they are, in fact, the lightest baryons, each made up of 3 quarks. Only the proton and anti-proton baryons are stable in isolation, but in nuclei protons plus neutrons can be stable together and anti-protons plus anti-neutrons can also be stable together.
Here's a good reference for subatomic elementary particles, where you can see some familiar names like electron and photon: https://en.wikipedia.org/wiki/Baryon#/media/File:Standard_Mo...
neutrons and protons are baryons (each made of 3 quarks)
electrons are leptons
photons are bosons
There are more things in those categories that are much less a part of the human experience.
Source: I am a smientist.