This chapter traces the evolution of the digital economy from early conceptions of ICT-enabled commerce to today’s data-driven, platform-centred ecosystems. We first clarify narrow and broad definitions adopted by international bodies and policy communities, then show how pervasive digitization has reshaped market structure and conduct. Multi-sided platforms lower entry barriers while amplifying network effects, often yielding oligopolistic dynamics and “winner-takes-all” outcomes. Data—characterized by high fixed and near-zero marginal costs, scalability, and spillovers—has emerged as a core competitive asset, enabling precision matching, rapid product iteration, and, in some cases, new levers of market power. We catalogue salient unfair practices observed in platform markets, including exclusivity arrangements, self-preferencing, data blocking, personalized (discriminatory) pricing, tying/bundling, strategic exploitation of network effects, and algorithmically facilitated coordination. These behaviors are frequently opaque and adaptive, complicating detection, proof, and timely remedies. We argue that traditional antitrust—anchored in price-centric market definition, static indicators of dominance, and ex-post casework—faces material limits when applied to zero-price services, cross-market leverage, and black-box algorithms. In response, jurisdictions have begun to modernize their toolkits. The EU has introduced ex-ante obligations for “gatekeepers” alongside horizontal platform governance rules; Germany has updated abuse control for firms of paramount cross market significance; the United States has refreshed merger guidance for digital markets; Japan has advanced transparency requirements for mobile ecosystems; and China has revised competition and data-governance statutes to address algorithmic and data-based abuses. We conclude by motivating a complementary “computational antitrust” agenda—combining procedural due process and rule-of-reason analysis with model-based screening, simulation, and audit of data and algorithms—to better balance innovation and fairness in the digital economy.