Whys is asterisk and random variable necessary in these functions?

[Gribouillis]

When you bind the callback to a key, it receives a KeyPress event parameter every time the key is pressed. On the other hand, a function bound to a Button does not receive a parameter when the button is pressed. So if you want to bind the callbacks both to a key and to a Button, you need to give them a variable number of arguments. Try adding a print() in the functions to see what it does

# Change text with "Enter" then flush
def changeTextEnter(*args):
    print('changeTextEnter:', args)
    text_label.configure(text=entry_bar.get())
    entry_bar.delete(0, tk.END)
 
# Close program key function
def quitApp(*args):
    print('quit:', args)
    main_window.destroy()

Output:
changeTextEnter: (<KeyPress event keysym=Return keycode=36 char='\r' x=89 y=14>,)
changeTextEnter: ()
quit: (<KeyPress event keysym=Escape keycode=9 char='\x1b' x=181 y=14>,)