title: Importing with dot notation
body: <p>Can someone explain this to me?
  When you import <code>Tkinter.Messagebox</code> what actually does this mean (Dot Notation)?
  I know that you can import <code>Tkinter</code> but when you import <code>Tkinter.Messagebox</code> what actually is this? Is it a class inside a class?</p>
  <p>I am new to Python and dot notation confuses me sometimes.</p>