The primary means of scripting in Unity is to write callback functions in classes derived from MonoBehaviour, which we know Unity will call when necessary. Perhaps the four most commonly used callbacks are Awake(), Start(), Update(), and FixedUpdate().
Awake() is called the moment MonoBehaviour is first created, whether this occurs during scene initialization or when a new GameObject instance containing the MonoBehaviour component is instantiated at runtime from a Prefab. Start() will be called shortly after Awake() but before its first Update(). During scene initialization, every MonoBehaviour component's Awake() callback will be called before any of their Start() callbacks are.
After this, Update() will ...
