Recursion HALP

Hey /prog/, I must say my understanding of recursion is shit (never really dealt with recursion in all my days of writing bad code). How should I go about thinking about it?

inb4 flaming: I understand the recursive concept in some contexts, such as when it is used in a factorial function, but when it starts getting more ambiguous (say, exercise 5, ch. 2 from ANSI Common Lisp) it's ugly.

inb4 RECURSE MY ANUS

>>10
There are a couple of ways a computer could solve an unpotimised recursive problem you fucking moron.  Of coure the only way you would know something like this is if you actually read something other than SICP.