The purpose of this text is to introduce engineering and science students to the basic underlying physics and chemistry concepts that form the foundation of plasma science and engineering. It is an accessible primer directed primarily at those students who, like the general public, simply do not understand exactly what a plasma or gas discharge is nor do they even necessarily have the fundamental background in statistical thermodynamics, gas dynamics, fluid dynamics, or solid state physics to effectively understand many plasma and gas discharge principles. At the conclusion of this text, the reader should understand what an ion is, how they move, the equations we use to describe these basic concepts, and how they link to the aforementioned topics of plasmas and gas discharges. This book is focused on specific concepts that are important to non-equilibrium, low temperature gas discharges. These discharges fi nd wide applicability today and are of significant interest to the scientifi c and engineering communities.