Here is an explanation of folds on lists: List Folds at BFPG
I only briefly read through the slides, so I can’t comment on the presentation, but I believe it should shed some light on the mystery of folds. Folds for Imperative Programmers is just what the title says. The code is in Scala, but it should be navigable.
I’ve read some of Tony’s other work and he knows his category theory concepts. His Monad Exercises in Scala (Haskell too) will change the way you think about programming.
