This document provides an overview of lasers and their applications in periodontics. It begins with definitions of key laser terminology and concepts like the acronym LASEr. It describes the historical development of lasers and the parts that make up a laser system. Different types of lasers are classified based on their wavelength, active medium, and safety level. The document discusses the interactions between laser light and tissue, including absorption, photothermal, and photochemical effects. Specific dental lasers like Nd:YAG, erbium, and diode lasers are described along with their characteristics and periodontal applications. Safety considerations are also covered.