Learning tkinter

[Rob Cliffe]

I am trying to learn tkinter.
Several examples on the internet refer to a messagebox class 
(tkinter.messagebox).
But:

Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:20:19) [MSC v.1925 32 
bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
 >>> import tkinter
 >>> tkinter.messagebox
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
AttributeError: module 'tkinter' has no attribute 'messagebox'
 >>>

Why is this?
TIA
Rob Cliffe