For a long time, it was highlighted that services have specific characteristics mainly used to differentiate themselves from goods. Proposed definitions and characteristics led to debates between specialists in economics, marketing and management for several years and result in different points of view and approaches. There is still no consensus in these disciplines. More recently, new ones have contributed to define the concept of service. The goal of this paper is to present, on the one hand, the existing literature proposed by economists and managers about services (definitions and specificities) and, on the other, perspectives proposed by other disciplines such as computer science, engineering science or the SSME that challenge them. The bibliographical analysis results in a conceptual modeling of service and service delivery.