http://haskell.cs.yale.edu/wp-content/uploads/2011/01/cs.pdf

pg 11 has information on the Y combinator. Wikipedia has a better explanation of the proof. https://en.wikipedia.org/wiki/Fixed-point_combinator#Fixed_point_combinators_in_lambda_calculus

Now I understand the proof, but I’m still confused on how it “simulates” recursion.