As more of our human interaction moves online and facilitated by digital channels, it becomes increasingly important to understand how being online influences how we interact with others and ourselves. This textbook introduces students to the fundamental concepts, theories, and applications of computer-mediated communication. To prevent information from being dated, the text begins by building a foundational understanding of CMC theories--including CFO, SIP, SIDE, and hyperpersonal--to understand how being online affects human-human communication in a way that is not dependent on or embedded in a particular channel. From there, subsequent chapters explore how CMC intersects with and affects other communication subdisciplines, including interpersonal, organizational, and intergroup. After exploring these intersections, the textbook considers various uses of CMC, including to persuade, to entertain, and to facilitate relationships. Though contemporary examples are offered to illustrate theories and application, the text is written in a way that allows and encourages scholars to think about their own media use in a broader and channel-agnostic mindset, applying what they learn beyond just Instagram and Snapchat, to make sense of their modern and digital world.