Recurrence
Recurrence is extremely important to understand since it's present in all things that exist physically and conceptually. Here you fill find what exactly is recurrence, why we need to understand it, how we can use it to our advantage.
WARNING
Recurrence will be an introductory lesson. It won't teach you any new software skills but will instead set you in the right mindset and will make you see why is important to observe and understand our world and its phenomenons.