In order for health services delivery to accelerate gains in health outcomes it must continuously adapt and evolve according to the changing health landscape. At present, the case for change is a compelling one. However, despite mounting attention put to reforming health services delivery, there remains a persisting lack of consensus on its conceptualization. This paper aims to take stock of the developments in the literature on health services delivery and lessons from the firsthand experiences of countries, viewing clarity on the performance, processes and system dynamics of health services delivery a prerequisite for the rollout, scale-up and sustainability of reforms. Through a mixed-methods approach, evidence from existing frameworks and tools for measuring services delivery, country case examples and commissioned papers have been reviewed around three key questions: what are the outcomes of health services delivery? How can the health services delivery function be defined? And, how do other health system functions enable the conditions for health services delivery?