In plain words
Every human being who has senses is naturally enveloped by the guṇas of sattva, rajas and tamas. The body weds only the guṇas. That is why Daśaratha delighted in Kausalyā, Sumitrā and Kaikā, who are the guṇas of sattva, rajas and tamas. So Kausalyā, Sumitrā and Kaikeyī are like the guṇas. Daśaratha is the embodiment of the ten senses. When such guṇas are there, resolves bound up with desire arise. The fruits of those desires are Rāma, Lakṣmaṇa, Bharata and Śatrughna.
These four sons are embodiments of the four Vedas. Rāma is the Ṛgveda, Lakṣmaṇa the Yajurveda, Bharata the Sāmaveda. Śatrughna is the Atharvaṇa Veda. This Rāma principle that is the Ṛgveda comes forth more fully in the Yajurveda and the Sāmaveda. This Ṛgveda is blended into all the Vedas. It is the embodiment of Dharma. The Yajurveda is the embodiment of mantra. Lakṣmaṇa is the one who passed his time ever in the thought of Rāma, keeping that mantra alone before his eyes. Bharata is the one who, unable to bear or endure separation from Rāma, sang Rāma's name without ceasing. That is why Bharata is the embodiment of the Sāmaveda. Lakṣmaṇa is the one who, giving up sleep and food day and night, took the ceaseless guarding of the Rāma principle as the very principle of his life. Śatrughna is the one who used all his strength, bore every kind of weapon and kept Rāma, Lakṣmaṇa and Bharata safe. He bore these weapons to protect Bhakti, strength and Dharma. The four Vedas, the Ṛg, Yajur, Sāma and Atharvaṇa Vedas, grew up playing like children in Daśaratha's home in Ayodhyā.
The very moment He entered Ayodhyā together with this Māyā Devī, Rāma went into the forest called life. All these mysteries belong only to those joined with this Māyā. Birth is nothing but what is joined with Māyā. So Rāma, joined with Māyā, entered the forest. The moment He entered the forest, He began to lose His Brahmajñāna. This Brahmajñāna took the form of Sītā. He went through separation from this Brahmajñāna. Resolving to take this Brahmajñāna back, He carried on the search. On the way, two brothers met Him. They were Vāli and Sugrīva. These Vāli and Sugrīva are wretchedness and Viveka, and between the two a fight went on without end. Rāma helped Viveka in order to destroy wretchedness. That is, He helped Sugrīva and destroyed the wretchedness called Vāli. With the help of the Viveka called Sugrīva, the courage called Hanumān became His friend. With the help of this courage and Viveka, He carried on the search for Sītā. That is, He carried on the search for Jñāna. On the way, the ocean of delusion stood across His path. It is full of delusion. He crossed this ocean of delusion. Could Rāma, who had conquered Māyā, not master delusion? The moment He crossed this ocean of delusion, the three guṇas, sattva, rajas and tamas, blocked His way. Vibhīṣaṇa is sattva, Rāvaṇa is the rajoguṇa, Kumbhakarṇa is the tamoguṇa.