[Tutor] Please explain part of this code

[Jim]

import sys
from notebook import Notebook, Note

class Menu:
     '''Display a menu and respond to choices when run.'''
     def __init__(self):
         self.notebook = Notebook()
         self.choices = {
                 "1": self.show_notes,
                 "2": self.search_notes,
                 "3": self.add_note,
                 "4": self.modify_note,
                 "5": self.quit
                 }

     def display_menu(self):
         print("""
Notebook Menu

1. Show all Notes
2. Search Notes
3. Add Note
4. Modify Note
5. Quit
""")

     def run(self):
         '''Display the menu and respond to choices.'''
         while True:
             self.display_menu()
             choice = input("Enter an option: ")
             action = self.choices.get(choice)
             if action:
                 action()
             else:
                 print("{0} is not a valid choice".format(choice))
<snip>

The author says:

The action variable actually refers to a specific method and is called 
by appending empty brackets (since none of the methods require 
parameters) to the variable.

I sort of understand what is going on with "action". All of the choices 
to the right of the :'s are methods defined elsewhere in the code. So I 
guess that will call whatever method is associated with a choice.

I don't recall ever seeing this before.  What is this technique called?

Thanks,  Jim