You'll never go hungry again

A function is a piece of the Script that can be executed, or called, over and over again. It's like having a sandwich that you can eat as many times as you want. We use functions to organize our code, and to house lines of code that we may need more than once.

The function we used is called Update. Just as there's an ongoing physics process in the background of our game that we can tap into to make our ball move and bounce, there's an ongoing Update loop as well. Update is eaten (or called) again and again and again while our game runs. Any Script lines, or statements, that we put inside the Update function tap into that loop.

Notice the way the Update function is declared. On a restaurant menu, we might declare that our Street-Fightin' Hoagie is a scrumptious offering of mile-high pastrami with lettuce, tomatoes, bacon, and cucumbers, topped with a fried egg, and slathered with mustard. We can declare a function much more simply. It starts with the word function, and adds the function name and a pair of round brackets. If our hoagie was a JavaScript function, it might look like this:

function Hoagie() {
}

Certain functions, like Start() and Update(), are special functions that are inherent to Unity. At the time of writing, Unity 3D does not have a built-in Hoagie() function, which means it's a custom function.