This video introduces the concept of a set as a well-defined collection of distinct objects, numbers, or things, using everyday examples like books in a library and letters of the alphabet. It covers set notation (∈ and ∉), and explains the different types of sets — finite, infinite, null/empty, singleton, subset, proper subset, universal set, and power set — with worked examples, including how to determine the number of subsets in a given set using (2^n).