Newbie shader and simulation

Thank you. I have read the documentation for amplify shader but most of the nodes don’t mean much to me becaus i don’t understand the terms they stand for. I am yet to find a really good tutorial that explains what most nodes do by themselves. Maybe you dont get what I mean. For example i drag out the World Normal node, It’s description states: “Per pixel world normal vector” and i dont understand from what pixel. From where is the pixel exactly pointing its vector from?
I lack the fundamental knowladge and would like to have a good starting point to learn from.