Learning theories may be differentiated according to which forms of learning are at the fore, such as the acquisition of declarative knowledge ("knowing what"), procedural knowledge ("knowing how") or contextual knowledge ("knowing why, where and when"). ###>□ Les média sont des objets (par exemple un livre), des équipements techniques (par exemple un chevalet de conférence) ou des configurations (par exemple système vidéo, ordinateur person­nel) permettant de stocker et de transmettre des messages.