This chapter provides an overview of the main ways in which the state intervenes in markets, including when it (i) establishes and enforces the regulatory environment, including competition law; (ii) acts as a buyer or supplier of goods and services; (iii) influences the choices of suppliers through state support; and (iv) supports the provision of public services by either privately-owned or publicly-owned enterprises. In addition, it describes the potential to distort competition of each of these state interventions and how they are addressed by the OECD Recommendation on Competitive Neutrality. It also presents the scope of the Recommendation.