This is an unofficial mirror of Tkinter reference documentation (based on Python 2.7 and Tk 8.5) created by the late John Shipman.
It was last updated in 2013 and is unmaintained. [More info]
The relief style of a widget refers to certain simulated 3-D effects around the outside of the widget. Here is a screen shot of a row of buttons exhibiting all the possible relief styles:
The width of these borders depends on the
borderwidth option of the widget. The above
graphic shows what they look like with a 5-pixel border;
the default border width is 2.