Conversion of biomass into multi-products started several centuries ago. However, the idea to conceptualize portfolios of bioproducts and their associate interwoven processes as a biorefinery in reference to petroleum refinery dated only from few decades. The metaphoric term of biorefinery is now close to realism since few existing facilities can already prefigure the perspectives of wide spread of commercial plants. However, due to its attractiveness the concept of biorefinery becomes a portmanteau word. Rigorous classifications are therefore required in order to improve the nomenclature of biorefinery concepts, facilities and systems and make them more discernable. This chapter contributes to recent efforts toward classification of biorefineries, by considering sustainability potentials and flexibility as additional criteria besides feedstock, conversion, platforms and final products. After analyzing the up to date classification system of biorefineries, additional criteria were proposed and discussed considering the main drivers of the development and wide deployment of biorefineries into market.