किं तद्ब्रह्म किमध्यात्मं किं कर्म पुरुषोत्तम। अधिभूतं च किं प्रोक्तमधिदैवं किमुच्यते ॥

kiṁ tad brahma kim adhyātmaṁ kiṁ karma puruṣhottama adhibhūtaṁ cha kiṁ proktam adhidaivaṁ kim uchyate

What is that Eternal, what Self -knowledge, what Action, O Purushottama? And what is declared to be the knowledge of the Elements, what is called the knowledge of the Shining Ones?

In plain words: Arjuna asks Krishna, whom he calls Purushottama (the highest being), to explain the terms he just used: the Eternal, knowledge of the Self, action, the physical world, and the gods.