One of the great things in computer programming is once you've taught a computer how to do
an action, you can call that function again. You give it a name and then you can call it.
That's really like extending the language. In the program we built, we learned how to
draw a square by moving and turning four times. We can take that function and give it a name,
draw a square, so that any time we want to do that, we simply say draw a square and it
will go back and invoke that function, that code. It will get done for us. We've added
that concept to our programming language.