Lord Visnu, the Supreme Self (atma), is the source of everything, as explained in the Vedanta-sutra: janmady asya yatah. Because Brahma was born directly from Lord Visnu, he is called atma-yoni
SB Canto 5
Śrī Śukadeva Gosvāmī continued: The first created being and most powerful demigod in this universe is Lord Brahmā, who is always responsible for developing universal affairs. Born directly from the Supreme Personality of Godhead, he dedicates his activities to the welfare of the entire universe, for he knows the purpose of the universal creation. This supremely powerful Lord Brahmā, accompanied by his associates and the personified Vedas, left his own abode in the highest planetary system and descended to the place of Prince Priyavrata's meditation.
Lord Viṣṇu, the Supreme Self (ātmā), is the source of everything, as explained in the Vedānta-sūtra: janmādy asya yataḥ (SB 1.1.1). Because Brahmā was born directly from Lord Viṣṇu, he is called ātma-yoni. He is also called bhagavān, although generally bhagavān refers to the Supreme Personality of Godhead (Viṣṇu or Lord Kṛṣṇa). Sometimes great personalities—such as demigods like Lord Brahmā, Nārada or Lord Śiva—are also addressed as bhagavān because they carry out the purpose of the Supreme Personality of Godhead. Lord Brahmā is called bhagavān because he is the secondary creator of this universe. He is always thinking of how to improve the situation of the conditioned souls who have come to the material world to enjoy material activities. For this reason, he disseminates the Vedic knowledge throughout the universe for everyone's guidance.
Vedic knowledge is divided into two parts: pravṛtti-mārga and nivṛtti-mārga. Nivṛtti-mārga is the path of negating sense enjoyment, and pravṛtti-mārga is the path by which the living entities are given a chance to enjoy and at the same time are directed in such a way that they can go back home, back to Godhead. Because ruling over this universe is a great responsibility, Brahmā must force many Manus in different ages to take charge of universal affairs. Under each Manu there are different kings who also execute the purpose of Lord Brahmā. It is understood from previous explanations that the father of Dhruva Mahārāja, King Uttānapāda, ruled over the universe because his elder brother, Priyavrata, practiced austerity from the very beginning of his life. Thus up to the point of the Pracetās, the kings of the universe were all descendants of Uttānapāda Mahārāja. Since there were no suitable kings after the Pracetās, Svāyambhuva Manu went to the Gandhamādana Hill to bring back his eldest son, Priyavrata, who was meditating there. Svāyambhuva Manu requested Priyavrata to rule over the universe. When he refused, Lord Brahmā descended from the supreme planetary system, known as Satyaloka, to request Priyavrata to accept the order. Lord Brahmā did not come alone. He came with other great sages like Marīci, Ātreya and Vasiṣṭha. To convince Priyavrata that it was necessary for him to follow the Vedic injunctions and accept the responsibility of ruling over the world, Lord Brahmā also brought with him the personified Vedas, his constant associates.
A significant word in this verse is sva-bhavanāt, indicating that Lord Brahmā descended from his own abode. Every demigod has his own abode. Indra, the King of the demigods, has his own abode, as do Candra, the lord of the moon planet, and Sūrya, the predominating deity of the sun planet. There are many millions of demigods, and the stars and planets are their respective homes. This is confirmed in Bhagavad-gītā. Yānti deva-vratā devān: (BG 9.25) "Those who worship the demigods go to their different planetary systems." Lord Brahmā's abode, the highest planetary system, is called Satyaloka or sometimes Brahmaloka. Brahmaloka usually refers to the spiritual world. The abode of Lord Brahmā is Satyaloka, but because Lord Brahmā resides there, it is also sometimes called Brahmaloka.