How to scrolldown a textbox using scrollbar widget tkinter

Application: Building a notes application (as an intro to GUI development in Python) which includes feature of a scrollbar to scroll through a textbox

Problem: I can't actually seem to scroll down through the textbox. I don't seem to get the grayed rectangle which lets me control the scrollbar and scroll up/down through the textbox

#importing necessary packages
from tkinter import *
from tkinter import font
from tkinter import ttk


#set up main window
root = Tk()

root.title("Notes")
root.geometry("400x650")



#functions

#functions to change all widget button's backgrounds when user hovers over it and leaves it
def enter_button(e):
    e.widget.config(background = "#D4D4D4")
    
#SystemButtonFace is default colour
def leave_button(e):
    e.widget.config(background = "SystemButtonFace")


#clear text in text-box

def clear():
    
    #delete all text from text_box
    text_box.delete(1.0,END)
    
def bold_it():
    
    #create font
    
    try: 
        
        
        bold_font = font.Font(text_box, text_box.cget("font"))
        bold_font.configure(weight = "bold")
    
        #creating tag called "bold" which bolds textll upon condition
        text_box.tag_configure("bold", font = bold_font)
    
        #creating a bold tag which highlights first character
        bold_tag = text_box.tag_names("sel.first")
    
        #condition for checking to see if tag is applied or not
        #in the first highlighted character
        #if tag is applied, remove the bold from first-highlighted text
        #- last highlighted text
        #"bold" needs to be matched in the tag
        if "bold" in bold_tag:
        
            text_box.tag_remove("bold","sel.first","sel.last")
        
        else:
        
            text_box.tag_add("bold","sel.first", "sel.last")
        
    except TclError: 
        
        pass

def italics_it():
    
    
    try:
    
        #create a font
        italics_font = font.Font(text_box, text_box.cget("font"))
        italics_font.configure(slant = "italic")
    
        #create a tag called "italic"
        text_box.tag_configure("italics", font = italics_font)
    
        italics_tag = text_box.tag_names("sel.first")
    
        #condition to see whether tag has been applies or not
        if "italics" in italics_tag:
        
            text_box.tag_remove("italics", "sel.first","sel.last")
        
        else: 
        
            text_box.tag_add("italics", "sel.first", "sel.last")
    
    except TclError: 
        
        pass



#frames
top_frame = LabelFrame(root, padx = 30, pady = 10)

button_frame = LabelFrame(root, padx = 30, pady = 10)

text_frame = LabelFrame(root, padx = 10, pady = 10)

bottom_frame = LabelFrame(root, borderwidth = 0, highlightthickness = 5)




top_frame.grid(row = 0 , column = 0)

button_frame.grid(row = 1, column = 0, pady = 10)

text_frame.grid(row = 2, column = 0, pady = 1)

bottom_frame.grid(row = 3, column = 0, pady = 3)


#labels, textboxes, buttons

#top_frame content
Notes_label = Label(top_frame, text = "Notes", fg = "black", font = 1, padx = 141)
Notes_label.grid(row = 0 , column = 0)

save_button = Button(top_frame, text = "save")
#padx increases distance between buttons


#button_frame content

#bold button
#the ideal is that if u press ctrl + b, the bold_button is pressed by itself
#rn, it's gonna be a highlight technique
bold_button = Button(button_frame, text = "B", padx = 4, pady = 2, command = bold_it)
bold_button.grid(row = 0, column = 0)

#italicsize button
italics_button = Button(button_frame, text = "I", padx = 4, pady = 2, command = italics_it)
italics_button.grid(row = 0, column = 2, padx = 15)

#text_box frame button
text_box = Text(text_frame, width = 45, height = 27)
text_box.grid(row = 0, column = 0)

#text_box frame content
main_scrollbar = ttk.Scrollbar(text_frame, orient = "vertical", command = text_box.yview)

main_scrollbar.grid(row = 0, column = 1)

text_box["yscrollcommand"] = main_scrollbar.set







clear_button = Button(bottom_frame, text = "clear", padx = 2, pady = 2, command = clear)
clear_button.grid(row = 0, column = 0, padx = 15, pady = 10)

save_button = Button(bottom_frame, text = "save note", padx = 2, pady = 2)
save_button.grid(row = 0, column =1, padx = 15, pady = 10)





#binding all buttons for changing colours when user hovers over it and leaves it
bold_button.bind("<Enter>", enter_button)
bold_button.bind("<Leave>", leave_button)
italics_button.bind("<Enter>", enter_button)
italics_button.bind("<Leave>", leave_button)
clear_button.bind("<Enter>", enter_button)
clear_button.bind("<Leave>", leave_button)
save_button.bind("<Enter>", enter_button)
save_button.bind("<Leave>", leave_button)


















# main program loop
root.mainloop()

here's an image of the problem image of problem

I would also be very grateful if one could explain the concept of scrollbar.set and like yview and why they are both needed for the scrollbar to work. Tutorials and videos don't seem to explain the concept, but just implement it