@dicey__'s notes about Cybernetics. Probably mostly just paraphrased, quoted, or jacked as a mnemonic exercise. It's not plagiarism because I'm not writing a paper or an article. These are my notes, this is how I actively read, and they're on the Internet for your potential (but by no means guaranteed) benefit.
Source one: "Cybernetics and Second-Order Cybernetics", Francis Heylighen, Free University of Brussels
Variety: a measure of the number of possible states or actions
Entropy: a probabilistic measure of variety