In plain words
When the Supreme Person, whom the Vedas make known, was born as the son of Daśaratha, the Veda itself came forth from Prācetasa as the Rāmāyaṇa!
“Just as the Paramātma, whom the Vedas make known, was born as the son of Daśaratha, so the Veda itself was revealed as the Rāmāyaṇa through the mouth of the great sage Vālmīki.”
Embodiments of Prema! The Rāmāyaṇa is the very Veda come down from heaven to earth. The Vedas are in four parts: the Ṛgveda, the Yajurveda, the Sāmaveda and the Atharvaṇa Veda. In the Rāmāyaṇa the Ṛgveda is Rāma, the Yajurveda is Lakṣmaṇa, the Sāmaveda is Bharata, the Atharvaṇa Veda is Śatrughna. The four Vedas themselves took the forms of these four brothers and played in Daśaratha's house. The Ṛgveda and the Yajurveda are made up of mantras for the rites of yajña, yāga and the like. That is why Viśvāmitra took Rāma and Lakṣmaṇa with him, to guard his yāga. For the fourteen years that Rāma lived in the forest, Bharata left Ayodhyā, lived in Nandigrāma and kept singing the Name of Rāma without a break. That is why Bharata has been called the embodiment of the Sāmaveda. Wherever rites of yajña and yāga are held, wherever the Name of God is remembered, the one who guards that place so that ghosts, spirits and demons cannot enter is Śatrughna, the embodiment of the Atharvaṇa Veda. So you must not think that the Veda and the Rāmāyaṇa are different from each other. The Rāmāyaṇa is the very essence of the Veda. The Veda is the very form of the Rāmāyaṇa.
The Rāmāyaṇa came into being precisely for the rise of man. Five thousand years have passed since the Mahābhārata took place. The Rāmāyaṇa took place even before that. If, after so many thousands of years, the Rāmāyaṇa still shines on in man's heart to this day, you can imagine how great its excellence and its sacredness are.