We refer to a model that uses mathematical programming to find an optimal quantity as an optimization model. Thus, an optimization model differs from an evaluation model in that it goes beyond simply evaluating the consequences of proposed alternatives: It actually identifies the "optimal" alternative. How does an optimization model accomplish this impressive task? In this age of readily available computing power and ever more user-friendly software, it is possible to build and use optimization models without a detailed understanding of the mathematics that underlie the answer to this question. To truly take advantage of this capability, however, it is necessary to have a basic understanding of some core concepts. The primary objective of this note is to introduce these concepts. This note is highly pragmatic; the companion note "The Mathematics of Optimization" (UVA-QA-0683) explores more deeply the mathematical foundations of the concepts and is designed for the user with the motivation and mathematical background to further explore the topic.