Main Classes of a New Game in Unreal Engine 4

I would like to know what are the Main Classes of a New Game in Unreal Engine 4

This is the first module you need to know well.

Take the time to read code in AActor, AHUD, APawn, etc, etc…

https://docs.unrealengine.com/4.26/en-US/API/Runtime/Engine/GameFramework/