Set theory is the very foundation of mathematics after logic. Did you know that mathematicians have formalized the entirety of mathematics just on the basis of logic and sets!? This proves the maturity and immense rigor this subject carries.
In this mini course, my aim is to help you understand what are sets and how to work with them in a myriad of ways. Sets are used all over mathematics and so it's important for you to master them early on. The variant of set theory covered here is commonly referred to naive set theory which is simply the easier version of the subject (hence called "naive").