But another is the supreme Puruṣa, called the Paramātman, who entering the three worlds, sustains, imperishable, the Lord.

The third Puruṣa, superior to the previous two. Uttamaḥ — the highest, the supreme. This one is anyaḥ — different, other. He is called paramātman — the supreme Ātman, transcendent to the kṣara/akṣara duality.

He āviśya (penetrates) the loka-traya — the three worlds (upper, middle, lower; or heaven, atmosphere, earth). He bibharti (sustains, maintains), being avyaya (imperishable) and īśvaraḥ (the supreme Lord, the controller). This is the first time the Puruṣottama is explicitly identified.