Since C# scripts are classes, how does Unity know to make some scripts components and not others? The short answer is that LearningCurve (and any script created in Unity) inherits from MonoBehavior (another class). This tells Unity that the C# class can be transformed into a component.
The topic of class inheritance is a bit advanced for this point of your programming journey; think of it as the MonoBehaviour class lending a few of its variables and methods to LearningCurve. Chapter 5, Working with Classes, Struct, and OOP, will cover class inheritance in practical detail.
The Start() and Update() methods that we've used belong to MonoBehavior, which Unity runs automatically on any script attached to a GameObject. The Start() method runs once when the scene starts playing, while the Update() method runs once per frame (depending on the frame rate of your machine).
Now that you're familiarity with Unity's documentation has gotten a nice bump, I've put together a short optional challenge for you to tackle!