The Lord is one without a second, advaita. Acyuta: the Lord never falls down. The distinction between Lord and ourself . . . we are also eternal living entities, and the Lord is also eternal. He's also a living entity, a person, just like us, but His name is Acyuta. He never falls from His position. But we living entities, sometimes we fall down. Just our material condition of life, this is our falldown. Therefore He's called advaitam acyutam anādi. And He has no beginning. He is the beginning of everything. The creation is from Him, but He has no creator. So advaitam acyutam anādim ananta-rūpam (Bs. 5.33). And He has got multi-forms. He can expand Himself.
The one expansion is that īśvaraḥ sarva-bhūtānāṁ hṛd-deśe arjuna tiṣṭhati (BG 18.61). He has expanded Himself to live with you within your heart. Īśvaraḥ sarva-bhūtānām. Not only that; another place it is described, eko 'py asau racayituṁ jagad-aṇḍa-koṭi (Bs. 5.35). One portion of the Lord . . . that is confirmed in the Bhagavad-gītā: ekāṁśena sthito jagat (BG 10.42). Jagat means this material world. That is being maintained by one of His plenary portions, which is called Paramātmā, or Garbhodakaśayī Viṣṇu, or Kṣīrodakaśāyī Viṣṇu.
So one portion of His plenary portion, He is within the material world. A material world means within the universe. Aṇḍāntara-stham. Aṇḍa, brahmāṇḍa, means this universe. This is not only one universe, but there are many millions of universes. So He's there. Advaitam acyutam anādim ananta-rūpam (Bs. 5.33). And aṇḍāntara-stham: He is within the universe. Aṇḍāntara-stha-paramāṇu-cayāntara-stham (Bs. 5.35): and He is within the atom also. Just, just imagine expansion of God. So advaitam acyutam anādim ananta-rūpam ādyaṁ purāṇa-puruṣaṁ nava-yauvanaṁ ca. Although He's the oldest of all, you'll find Kṛṣṇa always a young man. He's, from His face, we'll find a young boy, twenty to twenty-five years. Nava-yauvanaṁ ca. Vedeṣu durlabham. If you want to search out God by studying Vedas, it will be very difficult. Adurlabham ātma-bhaktau. But He's very easily available from His devotee.