This paper reviews the growing literature on social protection. While not new, the concept evolved remarkably in recent years. It is approached from a multitude of perspectives, and intersects with broader bodies of literature – particularly around public policy, pro-poor growth, rights, humanitarian strategies, and aid effectiveness – as well as feeding into specific programmatic issues (e.g. conditionality, targeting and transfer selection). This blend of challenges and approaches has often made debates elusive and polarized. The paper examines the evolution and definitions of social protection, and unbundles critical policy, institutional and implementation quandaries. Taken together, these considerations shape a set of context-specific models of social protection. The paper’s five core conclusions may help chart future directions for social protection research and practice.