The main tkinter module and its submodule ttk in Python 3 appear to contain identical widgets (i.e. Buttons, CheckButtons, etc.). 
So, when creating a button, one has the freedom to either use a tkinter.Button widget or a tkinter.ttk.Button. 
Do you know what is the difference between them? Why would you choose one or the other?
It is just a matter of the design of a GUI Window. So Tkinter is a really easy-to-use efficient and useful GUI toolkit. But it looks a bit outdated. Tkinter Ttk widgets are similar to that of Tkinter. It is basically a sub-module of Tkinter. So, in Tkinter Ttk, almost many widgets are the same but to use them is different. Tkinter Ttk widgets are more customizable and a lot of windows programs are done and designed using Tkinter
What is the difference between the widgets of tkinter and tkinter.ttk in Python?