I would say that the init handles things that you normally have to worry about on other platforms, but the Arduino does some things behind the scenes.
The init is an important part of this 'behind the scenes' and you should be thankful it's there. You normally do not need to know what it does.
The only thing to know, is that there are some things you can not do before the init has been called, so when the time comes fro writing libraries/classes then you need to refrain from doing certain things in the constructors as they might run before init has.