This document provides an overview of public address (PA) and sound reinforcement systems. It defines a PA system as an electronic sound amplification system using a microphone, amplifier, and loudspeakers to allow a person to address a large audience. A sound reinforcement system enhances live sound from vocals and instruments to distribute to a larger audience using a mixing console, microphones, processors, amplifiers and loudspeakers. The document discusses considerations for PA systems including room acoustics, audience size and location, and discusses the basic components and signal flow of both PA and sound reinforcement systems.