I'll focus on a side question, that I'm more prepared to answer.

Truthfully, everything besides that (including ‘what are proteins’) mostly wooshes over my head

At the end of the day, proteins are biiiiig arse molecules. Mostly composed of carbon, hydrogen, oxygen, and nitrogen. For example, here's a protein called "myoglobin", that carries oxygen within your blood:

Blue = nitrogen, red = oxygen, grey = carbon, white = hydrogen, salmon = iron, yellow = sulphur. Disregard the mix of sticks and balls in the model, they're both representing atoms.

If you pay close attention to the model, you'll notice a repetitive pattern: 1) nitrogen, 2) carbon connected to some large junk, 3) carbon connected to a "dangling" oxygen. That is not just in the myoglobin, but in all proteins.

If you flattened that pattern and removed the hydrogens (to simplify it), you'd get something like this:

That happens because the bodies of living beings don't build those huge molecules out of nowhere; they do it with smaller molecules called "aminoacids". That pattern there is the amide group, you could see it as the "solder" between aminoacids.

Here's the representation of a few "free" aminoacids:

The fun part is that R, the "side chain". I called it "junk" but it's actually a big deal - because it's what gives each protein a different shape and property. For example, it's thanks to that junk that the myoglobin has a specific shape, that forms a "ring" of nitrogens, just at the right size to host an iron cation, but still leaves one of the sides of the iron cation free - so it could connect to something else. (Hopefully diatomic oxygen. As in, it's how myoglobin transports that oxygen within your body. But if you get poisoned with carbon monoxide or cyanide, it gets stuck there, and it's hard to take it off so the protein stops transporting oxygen.)