In this recipe, you added an instance of the FadeAway scripted class to the Text-hello GameObject. Due to the RequireComponent(...) attribute, an instance of the CountdownTimer script class was also automatically added.
The Awake() method caches references to the Text and CountdownTimer components in the countdownTimer and textUI variables.
The Start() method reset the countdown timer so that it starts counting down from 5 seconds.
The Update() method (executed every frame) retrieves the proportion of time remaining in our timer by calling the GetProportionTimeRemaining() method. This method returns a value between 0.0 and 1.0, which also happens to be the range of values for the alpha (transparency) property of the color property of a UI Text GameObject.
It is often a good idea to represent proportions as values between 0.0 and 1.0. Either this will be just the value we want for...