Can someone help me understand post process materials?

I really like stylized kinds of scenes and I’ve found a good amount of post process materials that give me the effect that I like, but I’m feel like I have no idea what these are really doing when I try to use them in scenes I have. I see the scene texture node used quite a lot, and things are being divided, multiplied, desaturated, clamped, appended, and sometimes put back into other scene texture nodes or sometimes through if nodes to use custom depth rendering checks. I guess what I would really want to know, is what do the scene texture nodes properties really modify? If I can figure out what that does, maybe I might have a better understanding of how this node is being manipulated to do so many cool things.

One thing I did see was the stylized rendering pack, I’m interested to know what the square samples section for outlining is and how that works as well.

Below are a few links to help get you started. the first one is the post process doc, the second is a live training about basics, and the third is a bit more advanced. my advise would be to learn what certain nodes do by creating effects based on tutorials and playing around with the nodes to see what changes. also read the tooltips. as for the general settings either play with them, google about them, or learn a bit about photography. things like exposure and depth of field are something common in photography so learning a bit about that could help.