The focus of this lesson is not the most basic, but it is the most important in the entire course.
Python is often used to work with data all over the world. There may be a small amount of data that even a weak computer can handle. Or there may be so much data that you need entire computer clusters, groups of computers networked together to solve a common problem. We can handle that amount of information only with that amount of power.
There is even a wholeindustry, and Python is one of the main tools in machine learning, expert systems, and data mining, among other things. We should represent all data in computer memory in a way that makes it convenient and efficient to work with. Programs often store data in collections — a list of users, a list of pages, a list of dates, a list of strings, and a list of servers. We can represent all of these entities in code as collections.