The material world is shadow; the spiritual reality is eternal and is humanity's only worthwhile destination.Listen — Srila Prabhupada Uvaca
Prabhupāda: paras tasmāt tu bhāvo 'nyo 'vyakto 'vyaktāt sanātanaḥ yaḥ sa sarveṣu bhūteṣu naśyatsu na vinaśyati [Bg 8.20] [Yet there is another nature, which is eternal and is transcendental to this manifested and unmanifested matter. It is supreme and is never annihilated. When all in this world is annihilated, that part remains as it is.] Now, this verse we have been discussing from the last day. There is another nature, paras tasmāt tu bhāvaḥ.
Bhāva means nature, and para, para means superior. So there is another, superior nature, vyaktaḥ avyaktāt sanātanaḥ. Vyakta means what you see manifested. Now, this material universe you are seeing manifested...
Practically not seeing, but at least at night we can see how the stars are twinkling, so many planets, innumerable. This is manifested. And beyond that manifestation there is covering of the universe. Vyakta-avyakta.
And beyond that avyakta there is another, material nature, er, spiritual nature... So Kṛṣṇa is pointing out that that nature... Paras tasmāt tu bhāvo 'nyo 'vyakto 'vyaktāt sanātanaḥ. Sanātana means eternal.
This nature, this material nature, it has got its beginning and end. But that spiritual nature, that has no beginning and no end. How it is? You can understand by simple example.
Just like this sky, and in some insignificant part of the sky there is some cloud, and the cloud covers us. When there is cloud or snowfall we see everything is covered. But that covering is only an insignificant part of the whole sky. That covering is not for the whole sky.
Because we are very minute, small, so a few hundred miles, if it is covered, this sky, we see that everything is covered. Similarly, this material sky is within the covering, with the covering of mahat-tattva, matter. And as this cloud, when it is clear, the original sky you can see, similarly, this covering of material matter, when it begins... Just like cloud has beginning and end, similarly, this material nature has beginning and end. Just like your body: it has got its beginning and end—simply for some time.