So this is how it is: this region contains the colourless, utterly formless, intangible being that actually is, with which the realm of true knowledge 247D is concerned, seen only by reason, the pilot of the soul. Now since the mind of a god is nourished by reason and unmixed knowledge, so too is every soul that cares to receive what is proper to it. Eventually, beholding what is, the soul is delighted, and contemplating the truth, it is nourished and gladdened, until the revolution carries it around in a circle to the same place. In the revolution, soul has sight of justice itself, sound-mindedness and knowledge; not knowledge to which becoming is added, this is knowledge different under different circumstances, 247E concerned with what we normally call ‘things that are’; no, it is the knowledge of that which really is. And once the soul has, in like manner, contemplated and feasted upon the other things that really are, it descends once more into the inner heaven and goes home. And when soul arrives there, its charioteer stations the horses at the feeding stall, sets ambrosia before them and gives them nectar to drink. — Phaedrus 247c

Some exegetical points:

Nature of the Higher Realm: Plato describes a transcendent realm that is "colourless, utterly formless, intangible" and accessible only to true knowledge (epistēmē). This description emphasizes the abstract and non-physical nature of the One beyond being and non-being. In this metaphysical domain, the only faculty capable of perceiving this is reason (nous). Plato often characterises reason as the pilot or charioteer of the soul, guiding it towards true knowledge. This underscores the idea that reason, rather than sensory perception, is what allows the soul to apprehend the true nature of reality.

Soul’s Nourishment and Delight: The passage suggests that a soul that engages with its proper objects of contemplation—true and unchanging knowledge—receives nourishment and delight. This engagement involves a direct encounter with the Forms, such as Justice, Temperance (sound-mindedness), and Knowledge itself. For Plato, this intellectual nourishment is vital for the well-being of the soul, elevating it beyond the transient and imperfect physical world.

The Concept of Revolution: The "revolution" likely refers to the cyclical journey of the soul as it moves through the higher realms and back to the material world. This cyclic motion is a recurring theme in Plato's work, reflecting the soul's eternal quest for knowledge and its periodic engagement with the world of Forms. Also reflects the 'myth of the eternal return' which characterised the archaic Indo-European mythology. (c.f. Mircea Eliade)

Knowledge and Being: Plato makes a distinction between the knowledge of things that "become" (the sensory and changing) and the knowledge of "what is" (the "always so"). The former is seen as inferior because it is subject to change and decay, unlike the latter.

Descent of the Soul: After feasting upon the truths of the higher realm, the soul descends "into the inner heaven" and returns to the mundane world. However, this is not merely a return to ignorance; the soul retains a higher understanding acquired from its communion with the Forms. This journey reflects the dual nature of the Platonic soul, caught between the world of eternal Forms and the physical world. (Hence the logic of anamnesis - the soul recalling what it has learned but forgotten in the descent into birth.)

Ambrosia and Nectar: The reference to ambrosia and nectar, foods of the gods in Greek mythology, symbolizes the divine and immortal nature of the nourishment that the soul receives from its engagement with the Forms. This not only sustains the soul but also prepares it for its continuous cycle of rebirths and intellectual engagements. 'Nectar' is related to the Sanskrit 'amṛta' which means literally un (a-) dying (mṛta, the indo-european root of 'mortal' and also 'murder') and which is often translated as 'the nectar of immortality'.

Nature of the Higher Realm: Plato describes a transcendent realm that is "colourless, utterly formless, intangible" and accessible only to true knowledge (epistēmē). This description emphasizes the abstract and non-physical nature of the One beyond being and non-being. In this metaphysical domain, the only faculty capable of perceiving this is reason (nous). Plato often characterises reason as the pilot or charioteer of the soul, guiding it towards true knowledge. This underscores the idea that reason, rather than sensory perception, is what allows the soul to apprehend the true nature of reality. — Wayfarer

The logic of "being and non-being", represents the discrete nature of the reality of "now". At each moment as time passes, there is a true representation of what is and what is not at that precise moment. Since this is a static form, a true "what is" at each precise moment in time, it transcends the sensory realm of what we know as the physical world. Sensory perception gives us a projection of continuous activity, rather than discrete moments of "what is". It is only reason which can lead us beyond the illusion of temporal continuity which our material bodies present our conscious minds with, through the unreliable, and deceptive, sense organs.

This is the way out of Plato's cave. If you study Augustine, you'll see that he takes up this position very strongly. The importance of "the free will", is the strength of will power. The free will allows us to separate ourselves from the temporal world of sensory diversions, to focus on the eternal principles, "being and non-being", and the true nature of reality.