What is the general use of Awake(), Start(), Update(), FixedUpdate(), LateUpdate()?

This really is something that is well covered in the scripting reference, so I'll just link to the descriptions:

• Awake
• Start

Quoting from the docs:

The difference between Awake and Start is that Start is only called if the script instance is enabled. This allows you to delay any initialization code, until it is really needed. Awake is always called before any Start functions. This allows you to order initialization of scripts.

• Update
• LateUpdate
• FixedUpdate

LateUpdate is called after all Update functions have been called. This is useful to order script execution. For example a follow camera should always be implemented in LateUpdate because it tracks objects that might have moved inside Update.

Also note that LateUpdate is called after animations are applied - this means you can implement procedural animation in LateUpdate which modifies the pose sampled by the animation system.

FixedUpdate is called every fixed framerate frame, if the MonoBehaviour is enabled. FixedUpdate should be used instead of Update when dealing with Rigidbody. For example when adding a force to a rigidbody, you have to apply the force every fixed frame inside FixedUpdate instead of every frame inside Update.

I hope that helps. You can read more about overridable functions on the scripting reference page for MonoBehaviour.

You can also read here about the Update Order.