EXCITING VOCABULARY TIME!
1. BIG, EXCITING WORDS
        A. Constructor: A procedure that combines data
        B. Selector: A procedure that retrieves data
        C. Procedure: A set of instructions that performs a task
        D. Function: A procedure which, given a set of inputs, will
           ALWAYS return the same output. 

Example: Given a procedure, f. If this is possible:

> (f 0)
3
> (f 0)
7

then f cannot be a function. A function would ALWAYS return the same value for the input 0.