We want to highlight the central role played by the notion of model in philosophy of science. Having first underlined the intricate tie existing between models and theories in science, we distinguish, in the philosophical literature, the notion of model as general conception from the structural notion of model currently encountered. We present in informal fashion and critically assess the main approaches adopted by epistemological analysis in its intent to characterize models generally associated with scientific theories. Lastly, and with a view to illustrating the centrality of the notion of model, we show how the current debate over scientific realism essentially hinges on contrasting ways to construe of models. Key words: model, theory, semantic view of scientific theories, scientific realism