Platform-based competition has fundamentally transformed competitive dynamics in digital markets by shifting the locus of rivalry from firm-level products to multi-sided ecosystems sustained by network effects and orchestrated participation. This integrative review synthesizes theoretical and empirical insights from peer-reviewed scholarship to examine how digital marketplaces, network externalities, and ecosystem strategies reshape value creation, competitive advantage, and strategic positioning. Early foundations in two-sided market theory established the centrality of cross-side and same-side network effects in driving platform scale and winner-take-most outcomes. Subsequent scholarship advanced understanding of platform envelopment, multihoming, complementor dynamics, and governance tensions between openness and control. The review identifies persistent strategic paradoxes: platforms must simultaneously encourage generativity to fuel innovation while safeguarding value appropriation and architectural integrity. By organizing the literature into a conceptual synthesis, the paper illuminates the interdependent layers through which platform leaders coordinate users and complementors, navigate openness-control trade-offs, and evolve in response to competitive feedback. Contributions include bridging fragmented perspectives across strategy, information systems, and economics, highlighting the temporal evolution from network effects to ecosystem orchestration, and delineating future research directions for platform evolution amid rapid technological change and regulatory scrutiny. The analysis underscores that sustainable competitive advantage in platform markets derives less from proprietary assets than from dynamic capabilities in governance, orchestration, and adaptive ecosystem design.