In plain words
They gave this one the names Viṣṇu, Vaiśvānara and Virāṭ-svarūpa too. That is, this Virāṭ-svarūpa is the one with many forms and names. When it is said that Kṛṣṇa showed Arjuna the Virāṭ-svarūpa, what does it mean? It is only to show this truth: that everywhere, at all times and in all conditions, He has taken on this form. The whole world is the very Viśva-svarūpa of God. This itself they have also called Virāṭ. In the Virāṭ-svarūpa, the Ātma in the waking state has taken on the gross form. That same one, in the dream state, has taken on the subtle form. In this waking state this Ātma, joined with the many senses, stands turned within and resolves of itself, as if saying ‘Ekohaṃ bahuśyām’; resolving within itself, it showed itself experiencing many forms and many states.
In this dream it keeps creating forms that are no forms, sounds that are no sounds, food that is no food, and such things. It is limited too. This creation is confined to that dream state alone; it does not belong in turn to any other state. It does not spread out again. But by itself it creates everything, and by itself it keeps experiencing fear, joy, many kinds of hardship and loss, pleasure and sorrow. The Ātma alone is the cause of it all. If ten people sleep in a room, ten kinds of dreams may come to the ten, but between one dream and another there is no connection at all. That is, by his own feelings alone he resolves and goes through a limited state, in the dream state. There a light is present which is the basis of all of these. This very light they called tejas. The Ātma whose form is tejas they named Taijasa. In the dream state the Ātma is there in the form of Taijasa.
A small example. We need not go as far as a dream. If you shut your eyes tight and inquire what we are seeing, nothing is seen. We say, “It looks like a great darkness.” But who is it that sees this darkness? If no one were seeing there, how could we decide that this is darkness? So even when the eyes are closed, because someone or other is seeing there, it is dark, it is black; there is someone who sees that blackness. There is someone who sees that darkness. That one is the embodiment of tejas. The one who is in the dream state in the Taijasa form has taken on the subtle form in the antaḥkaraṇa.
Then the third is suṣupti. That is, sound sleep. There is no jāgrat and no svapna at all. In it neither imagining nor creating is seen at all. All the senses have merged in the Manas.