This is the first of a series of papers that review the state of knowledge and practice regarding compensation and rewards for environmental services in the developing world. The paper begins with an assessment of the historical development of compensation and reward mechanisms within a broader context of changing approaches to nature conservation and environmental policy. The assessment shows that greater interest in compensation and reward mechanisms has emerged within a policy context of changing approaches to nature conservation and flexible multi-stakeholder approaches to environmental management. In the developing world, an even greater variety of perspectives has emerged on the opportunities and threats for using compensation and rewards for environmental services. Within that background, the paper clarifies key concepts - including the distinction between compensation and reward - and presents a conceptual framework for typifying and characterizing different types of mechanisms that link ecosystem stewards, ecosystem service beneficiaries, and intermediaries.