This book primarily design to understand plasma physics and surface modification by plasma nitriding. Plasma is popularly known as the fourth state of matter prevailing more than 99% of our universe; we, residing in earth belong to the tiny rest. American chemist Irving Langmuir first introduced the word “plasma” to electrical discharges during 1926-28. Plasma has drawn attention to scientists, engineers, biotechnologists and industrialists since it had been popular for basic study, application science, a source of generation of energy for future and considered as a frontier between physicists and technologists. The tremendous potential delivered in this novel field has lead to new ways of producing plasma, fascinating materials, fusion energy, numerous patents and various industries. The optical diagnostic widely known as OES has been widely utilized to glow discharge for its simplicity for identifying the plasma species. Plasma assisted nitriding or simply plasma nitriding (PN) is a new type of surface modification technique. It was first discovered in Germany in 30’s.