Tkinter 8.5 reference: a GUI for Python

A theme is a complete “look and feel,” customizing the appearance of all the widgets.

A style is the description of the appearance of one kind of widget. Each theme comes with a predefined set of styles, but you can customize the built-in styles or create your own new styles.

The phrase “kind of widget” in the previous paragraph technically refers to the “class” of a widget. However, in the ttk world, this is different from Python classes. Within ttk, the class of a widget is a character string. For example, the ttk class of a stock Button widget is the string 'TButton'.

Each style is composed of one or more elements. For example, the style of a typical button has four elements: a border around the outside; a focus element that changes color when the widget has input focus; a padding element; and the button's label (text, image, or both).

Section 48, “Finding and using ttk themes”.

Section 49, “Using and customizing ttk styles”.

Section 50, “The ttk element layer”.