In this essay, I consider the notion of game as a way of providing a structure able to modelize human activity in a broad sense, and didactic activity in particular. I attempt to show some aspects of this scientific relevance, as it is used within the joint action theory in didactics. I thus present the notion of game as a tool for describing practice, that is to say as a constitutive element of a theory of practice. In that way, the main function of model of game consists in explaining and understanding practice. After having presented some background elements on which rely, in my opinion, a fruitful use of the notion, I try to dissipate some ambiguities linked to the notion, in order to clarify the meaning of the expression “using a game model”. I then attempt to give to see some generic interests of the use of the game model, before quickly presenting some features of this use while comparing to those of task and activity. The conclusion focuses on the building of criteria of use of the game model.