Social dilemmas can exist at many different levels, from interpersonal relationships to decision making in large group settings.
Social dilemmas come in two forms, including commons dilemmas and public goods dilemmas.
In commons dilemmas individuals share access to a common resource like trees, fish, or water, and they must decide how much of that resource to use. It is in each individual's own best interest to use as much of the resource as possible, yet, if all do this, the resource will be seriously threatened. Thus, at the group level, it is best for individuals to restrain their level of harvesting. In public goods dilemmas individuals must decide how much of some valued resource such as time, effort, or money to contribute in an attempt to provide a public good. The essence of such public goods dilemmas is that each individual is tempted to free-ride on the contributions of others, but if all do so, all end up worse off than if all had decided to contribute.