This chapter develops a reflection on the theme and the different meanings that simulation can assume in applied research ambits, and deals with the problems connected to the lack of a specific ontology shared by the scientific community. In this context, after the reflections on the interconnections between simulation and reality with a view to integrating rather than superimposing one on the other, we propose a classification for simulation in the educational field that takes the didactic, social and political literature into account and underlines the need to construct an ontology that can overcome the semantic ambiguity and support a scientific debate, with particular reference to simulation games seen from the perspective of the ecology of human development.