In real life, there are numerous situations where we need to collect the objects according to their characteristics or attributes and study those particular classes. This chapter deals with the concepts of sets, types of sets, operations, Venn diagram, algebra of sets, Inclusion-Exclusion Principles and Mathematical Induction. The chapter explains each concept by using the “BEIMI” philosophy. The example of the library system helps to enhance the understanding of the concepts of Inclusion and exclusion principles. It also explains how the cooking of any food is connected to the principle of Mathematical Induction. The theory is supported by precise real-life examples for meaningful understanding of the concepts. The chapter concludes with case studies, projects and exercises aimed at connecting theoretical relational structures to real-world applications across various disciplines.