A 'for' loop.

Imagine you have a bunch of books on a shelf, and you want to read each book one after the other. 

A 'for' loop in Python is like having a friendly book-reading robot that helps you with this task.

Here's how it goes:

You tell the robot how many books you have, so it knows when to stop. Then, you ask the robot to read each book for you, one by one, and you can do something with each book as it's read.

books = ["Harry Potter", "Matilda", "Charlotte's Web", "Percy Jackson"]

for book in books:
    # 'book' is the name of the book the robot is reading at the moment
    print("Reading", book)
    # You can do more stuff with the book, like taking notes or telling a friend what it's about!

Did you get all of that?

books is a list of book titles
and in the 'for' loop we created a variable named 'book'.

and now 'book' will represent each title in our list of 'books'.
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Side note: If you want to make a loop that will just run x times, you do this:
for x in range(10):
    print(x)

The 'x' can be anything, and the number '10' can be any number.