In the digital era, where human and algorithmic decision-making are intertwined, Game Theory takes on new meaning. It is no longer merely a formal theory of rational strategies, but is becoming a language for understanding interactions among humans, autonomous systems, and digital platforms. The player is no longer exclusively human, and equilibrium shifts from a fixed point to a process of continuous adaptation and learning. This book explores how Game Theory extends beyond traditional economic frameworks to encompass artificial intelligence, multi-agent systems, education, and digital society. It demonstrates that game-theoretic models are no longer merely objects of analysis, but actively shape the behavior of users, communities, and technological systems. The book invites readers to reflect on how games function as formal models, technological artifacts, and social phenomena; how Game Theory and digital society co-shape one another; and how this relationship is transforming how we think, communicate, and make decisions today.