Let me write here about some important places, where Lord Vishnu resides in His various forms:-
Vaikunth - In Vaikunth lok, Lord Vishnu resides in His four handed form with Goddess Laxmi. It is like a kingdom. Others living with Vishnu there serve Him and they are happy to serve Him.
There is Vaikunth in the spiritual world, which is eternal i.e. it remains even when the universe is destroyed. For the welfare of His devotees, Lord Vishnu also manifests Vaikunth lok inside the universe.
Golok - In Golok, Lord Krishn resides eternally with Radha and gopas and gopis. They are always happy, signing and dancing are are free of worries. Gopas and gopis in Golok do not treat Krishn as higher than them. They are not in awe of Krishn. They are not at all concerned that Krishn creates so many universes (which is same as saying that Vishnu creates so many universes). For them, creation of universes is of no significance. They just know that Krishn is their beloved friend and they play with Him.
Saket - Lord Ram eternally lives in Saket dham with Sita and with His devotees who served Him during His Ram incarnation on Earth. All inhabitants of Saket know that Lord Ram is supreme and they happily serve Him.
Some people call the three above combined as Vaikunth. According to this classification, Golok, Saket and Vaikunth described above are parts of Vaikunth. However, this is only the matter of definition and the meaning is the same.
Causal Ocean - This is also called as Viraj river. Maha Virat resides there. He is also known as Maha Vishnu, Karanodakshayi Vishnu, Karanavasayi Vishnu. He is all alone. Not even Laxmi and Sheshnag are there with Him. As He breathes in and out, multiple universes are created from the pores in His body. There are many universes but there is only one causal ocean and only one Maha Virat, who is the cause of multiple universes.
Garbhodak Ocean - Inside each universe, there is a garbhodak ocean. Lord Laghu Virat lives there on Sheshnag and with Laxmi. He is also known as Garbhodakshayi Vishnu. The word "laghu" means small and the word "virat" means big. He is very big in size but smaller than Lord Maha Virat. Therefore, He is called as Lord Laghu Virat. From Laghu Virat's navel, a lotus comes out. Lord Brahma comes out of this lotus.
Ksheer Sagar (ocean of milk) - Lord Kshirodakshayi Vishnu lives in the ocean of milk with Laxmi on Shesh Nag. When gods go to pray to Him, then they do so from the shore of the ocean or from an island called Shvet Dvip inside this ocean. Lord Kshirodakshayi Vishnu comes out of the ocean on hearing their prayers.
There are more, but above are the most prominent ones.
Kyunki Saas Bhi Kabhi Bahu Thi 2
Bade Achhe Lagte Hain
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