This document provides an overview of several theories related to public relations and communication including: systems theory which discusses how organizations and their environments depend on each other; situational theory which examines how problem recognition, constraint recognition, and involvement impact engagement; social exchange theory which explores how individuals choose strategies based on perceived costs and benefits; diffusion of innovation which explains how new ideas and behaviors are adopted; uses and gratifications theory which considers how and why people use media; and social learning theory which discusses how people learn from examples in mass media and from other people.