[Tutor] Variable in tkinter?

[Jim Byrnes]

I have been working my way through a Python 3 book and got to the 
chapter on tkinter. The following is a segment of a example program that 
works:

# the views
frame = tkinter.Frame(window)
frame.pack()
button = tkinter.Button(frame, text='Up', command=click_up)
button.pack()
button = tkinter.Button(frame, text='Down', command=click_down)
button.pack()
label = tkinter.Label(frame, textvariable=counter)
label.pack()

when I first looked at it I thought it would not work, thinking that the 
second reference to button = would over write the first one. Obviously 
that is wrong because the program does work.  Could someone explain to 
me why it works?

Regards,  Jim