Multi-agent systems involve agents interacting with each other and the environment and working to achieve individual and group goals. The achievement of group goals requires that agents work together within teams. In this paper we first introduce three philosophical approaches that result from different answers to two key questions. Secondly we consider three theoretical frameworks for modelling team behaviour. Next we look at two agent implementation models. Finally, we consider one of those implementation models — JACK Teams — and place it in the context of the philosophical debate and the theoretical frameworks.