Function Definitions

Function definitions are really hard to understand just from the book. I didn't get the whole "bruce" thing. I think I get it now, though.
A function definition is like a variable for a function. For ex/
if you type
def print_twice(x):
print x, x

then
print_twice('dog')

it will print
dog dog

The statement (print_twice) is a variable for the function (print x, x). The parameters(x) are variables that change the result of the function depending on what you enter into the parenthesis. ('dog') prints dog, dog if I type ('cat') it prints cat, cat.

That's how I would explain function definitions at least.