[Python] Protocols in tkinter in Python

I am new in Python and I want to use protocols like WM_DELETE_WINDOW, WM_TAKE_FOCUS and WM_SAVE_YOURSELF. I have found an example of WM_DELETE_WINDOW which is clear enough to understand. But I want to understand the rest two protocols. What do they do?

from Tkinter import *
import tkMessageBox

root = Tk()

def on_closing():
if tkMessageBox.askokcancel("Quit", "Do you want to quit?"):
root.destroy()

root.protocol("WM_DELETE_WINDOW", on_closing)

root.mainloop()

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