There are few concepts that are more central to natural resource management than those of property and property rights. Given their importance, it might be expected that there would be some consensus in the economic literature about what property and property rights are. However, no such consensus seems to exist. In fact, different authors use the same terms to denote quite disparate concepts and ideas, impeding rather than advancing progress in understanding natural resource management. As but one example, there is hardly a concept that has been as fundamentally misunderstood as that of the commons. That misunderstanding notwithstanding, there is another, less familiar, more common and even more fundamental one: the persistent confusion of possession with property. This article argues that the distinction between possession and property is of particular importance for comprehending the meaning of institutional shifts from one resource management regime to another. It therefore reviews concepts central to natural resource management, by distinguishing between state, private, common property and possession on the one hand and open access on the other.