This is an introduction to recursion that gently slopes toward tree recursion.
Traditionally, recursion is really hard for students to understand, and is taught fairly quickly. Divide and Conquer aims to walk the reader through the process of learning to think recursively at a manageable pace. There's a short preface about functions as well.
The only knowledge required is basic python. Specifically, you should know how if/else, functions, and while loops work.