Help me understand this... (Classes and self).

[Yoriz]

Here are some buttons added to two different frames, 1 button is added inside the class the other is added outside of it.

import tkinter as tk

class MainFrame(tk.Frame):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.pack()
        button = tk.Button(self, text='button1')
        button.pack(side="top")
        
class AnotherFrame(tk.Toplevel):
    def __init__(self, parent=None):
        super().__init__(parent)
        button = tk.Button(self, text='button3')
        button.pack(side="top")


root = tk.Tk()
main_frame = MainFrame(root)
button = tk.Button(main_frame, text='button2')
button.pack(side="top")
another_frame = AnotherFrame(main_frame)
button = tk.Button(another_frame, text='button4')
button.pack(side="top")

root.mainloop()