Python comes with a feature that is rarely shipped with a programming language: a built-in graphical user interface (GUI) library.
Python ships with a working version of the Tk widgets toolkit, which can be controlled through the tkinter module provided by the standard library.
The Tk toolkit actually is used through a simple language called Tcl. All Tk widgets can be controlled through the Tcl commands.
Most of these commands are very simple, and take the following form:
classname widgetid options
For example, something such as the following would lead to a button (identified as mybutton) with a red "click here" text:
button .mybutton -fg red -text "click here"
As those commands are usually relatively simple, Python ships with a built-in Tcl interpreter and uses it to drive the Tk widgets.
Nowadays, nearly everyone, even the more hardcore...