title: plus and non-plus for id-beginner wonder
body: <p>I am an Android beginner and I don't understand what exactly the plus (+) before <code>id</code> reference means.
  The tutorials I found on the web only say it is for <code>new id reference</code> and non-plus definition means it references the defined <code>id</code>. Could you offer an example to clarify my non-understanding of this tiny detail I am cracking my brain to get it right ?</p>