What is the purpose of using the `self` parameter in Python class?

I have been taking a Python OOP (Object Oriented Programming) course in which the instructor has taught me to use the self parameter in every function and with every variable when I must develop a class. Here is the Python class code below that I got during this course.

In the above code, every function contains a self parameter, also every variable is linked with the self keyword. I don’t know exactly what the purpose is of using the self parameter in classes. I would appreciate it if someone explained it to me.