The psychic function that perceives possibilities inherent in the present. (Compare sensation.)
Intuition gives outlook and insight; it revels in the garden of magical possibilities as if they were real.[“The Psychology of the Transference,” CW 16, par. 492.]

In Jung’s model of typology, intuition, like sensation, is an irrational function because its apprehension of the world is based on the perception of given facts. Unlike sensation, however, it perceives via the unconscious and is not dependent on concrete reality.

In intuition a content presents itself whole and complete, without our being able to explain or discover how this content came into existence. Intuition is a kind of instinctive apprehension, no matter of what contents. . . . Intuitive knowledge possesses an intrinsic certainty and conviction.[“Definitions” CW 6, par. 770.]

Intuition may receive information from within (for instance, as a flash of insight of unknown origin), or be stimulated by what is going on in someone else.

The first is a perception of unconscious psychic data originating in the subject, the second is a perception of data dependent on subliminal perceptions of the object and on the feelings and thoughts they evoke.[Ibid., par. 771.]