The concept of optimization is an inherent part of every human life activity and goals. It is a major part of the sustainability goals being practiced worldwide. This chapter covers the basic concepts involving the optimization domain. The basic steps in the optimization problem formulation are covered in detail along with simple, yet real-world examples. The concepts such as convexity and types of functions have been elaborated on with examples. The chapter also provides the basic optimization problem formulation such as the single-objective problem and its variation referred to as multi-objective problem along with examples. Furthermore, the general classification based on variables and problem types is also provided.