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

>>7
And just for the record you little fucking nigger, your shit example could give people the wrong idea about how recursion could work. This is because not every fucking programming language handles recursion the same way. This is partially due to the fact that the definition of a "variable" tends to vary.