This document provides an introduction to a course on interpersonal communication. It discusses several key concepts, including: 1) Nonverbal communication accounts for over 80% of messages conveyed, including social artifacts created both online and offline. 2) Effective communication is important for career success, relationships, and health. Improving communication skills can help address many interpersonal problems at their root. 3) The transactional model of communication describes how any change to one element of communication affects all other elements in a dynamic system. The "butterfly effect" demonstrates how small changes can have large consequences.