From the world of Brahman downward, all worlds are subject to return, oh Arjuna! But having attained Me, oh son of Kuntī!, there is no more birth.

Up to brahma-bhuvana — world of Brahmā, the creator of the present universe. Its residents live for eons but eventually are punar āvartinaḥ — returning, reincarnating.

mām upetya — coming to Me (Kṛṣṇa, the personal Supreme Lord), na vidyate punar janma — there is no more birth. Complete liberation is only in the personal Lord, not in elevated but material loka (worlds).