Over the past 30 years, numerous scholars in economics and management have studied a phenomenon we now refer to as 'platforms' - digital businesses that link multiple market sides and generate network effects within and across those market actors. In this literature review, we discuss the different definitions of the term 'platform' and explain the results of a bibliometric analysis of 578 peer-reviewed articles published on this topic during the past three decades. Based on a study of keywords, we organise the research into seven streams (strategy, architecture, governance, business model and customer relations, multi-platform bundles, ecosystem participants, and technological innovation) and three levels of analysis (business, corporate, and ecosystem). We conclude with some statistical summaries and comments.