The difference (between Lord Siva and Lord Visnu) is like that between milk and curd. Curd is nothing but milk, and yet it cannot be used in place of milk

Expressions researched:
"The difference is like that between milk and curd. Curd is nothing but milk, and yet it cannot be used in place of milk"

Srimad-Bhagavatam

SB Canto 1

The difference is like that between milk and curd. Curd is nothing but milk, and yet it cannot be used in place of milk.

SB 1.3.5, Translation and Purport

This form [the second manifestation of the puruṣa] is the source and indestructible seed of multifarious incarnations within the universe. From the particles and portions of this form, different living entities, like demigods, men and others, are created.

Lord Viṣṇu is nondifferent from the Personality of Godhead. Lord Śiva is in the marginal position between the Personality of Godhead and the living entities, or jīvas. Brahmā is always a jīva-tattva. The highest pious living being, or the greatest devotee of the Lord, is empowered with the potency of the Lord for creation, and he is called Brahmā. His power is like the power of the sun reflected in valuable stones and jewels. When there is no such living being to take charge of the post of Brahmā, the Lord Himself becomes a Brahmā and takes charge of the post.

Lord Śiva is not an ordinary living being. He is the plenary portion of the Lord, but because Lord Śiva is in direct touch with material nature, he is not exactly in the same transcendental position as Lord Viṣṇu. The difference is like that between milk and curd. Curd is nothing but milk, and yet it cannot be used in place of milk.

The next incarnations are the Manus. Within one day's duration of the life of Brahmā (which is calculated by our solar year as 4,300,000 x 1,000 years) there are fourteen Manus. Therefore there are 420 Manus in one month of Brahmā and 5,040 Manus in one year of Brahmā. Brahmā lives for one hundred years of his age, and therefore there are 5,040 x 100 or 504,000 Manus in the duration of Brahmā's life. There are innumerable universes, with one Brahmā in each of them, and all of them are created and annihilated during the breathing time of the puruṣa. Therefore one can simply imagine how many millions of Manus there are during one breath of the puruṣa.

The Manus who are prominent within this universe are as follows: Yajña as Svāyambhuva Manu, Vibhu as Svārociṣa Manu, Satyasena as Uttama Manu, Hari as Tāmasa Manu, Vaikuṇṭha as Raivata Manu, Ajita as Cākṣuṣa Manu, Vāmana as Vaivasvata Manu (the present age is under the Vaivasvata Manu), Sārvabhauma as Sāvarṇi Manu, Ṛṣabha as Dakṣasāvarṇi Manu, Viṣvaksena as Brahma-sāvarṇi Manu, Dharmasetu as Dharma-sāvarṇi Manu, Sudhāmā as Rudra-sāvarṇi Manu, Yogeśvara as Deva-sāvarṇi Manu, and Bṛhadbhānu as Indra-sāvarṇi Manu. These are the names of one set of fourteen Manus covering 4,300,000,000 solar years as described above.