Creating a frame with 4 command buttons

[Heyjoe]

Thanks all.

I have changed the code and it works.

I created this code after watching tutorials on classes and Tkinter.

There is still one thing that makes absolutely no sense to me. The second to the last line of code.

b=Main(root)

Why is Main(root) assigned to the variable? What does this line of code mean? Why does my code not work without this line of code?