The common sense (ḥiss mushtarak) is traditionally treated as the shared site of the sense-forms delivered through the external senses. Imagination retains those forms when the objects are absent, while the compositive or cogitative faculty separates and recombines preserved images and certain particular meanings.
Someone may have observed a tree, a blue sky and a bird on separate occasions, then mentally compose them into one scene. That composition differs from immediate vision. This internal meeting-place helps explain how the mind can link two statements.