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

>>30
"Therefore it could be a "C/C++" variable"

Okay, it's about time you answered the question.

"would end up as (* 5 (* 4 (* 3 (* 2 (1))))) before the evaluation of the products"

No, that isn't how it works if you define a variable in the C/C++ sense. Now before you get your panties in a bundle about this one, write a simple recursive fact program in C++ and then have it do something like the factorial of 2000! Do you get an exact number? I don't.