From Wikipedia

Introverted intuition is the intuition that acts in an introverted and thus, subjective manner. Jung wrote: “Intuition, in the introverted attitude, is directed upon the inner object, a term we might justly apply to the elements of the unconscious. For the relation of inner objects to consciousness is entirely analogous to that of outer objects, although theirs is a psychological and not a physical reality. Inner objects appear to the intuitive perception as subjective images of things, which, though not met with in external experience, really determine the contents of the unconscious, i.e. the collective unconscious, in the last resort. […] Although this intuition may receive its impetus from outer objects, it is never arrested by the external possibilities, but stays with that factor which the outer object releases within. […] Introverted intuition apprehends the images which arise from the a priori, i.e. the inherited foundations of the unconscious mind. These archetypes, whose innermost nature is inaccessible to experience, represent the precipitate of psychic functioning of the whole ancestral line, i.e. the heaped-up, or pooled, experiences of organic existence in general, a million times repeated, and condensed into types. Hence, in these archetypes all experiences are represented which since primeval time have happened on this planet. Their archetypal distinctness is the more marked, the more frequently and intensely they have been experienced. The archetype would be—to borrow from Kant—the noumenon of the image which intuition perceives and, in perceiving, creates.”