While describing the qualities that attract Krishna, Krishna emphasized the importance of developing the quality of equanimity in the presence of various circumstances in this world. Therefore, Arjuna now wants to deepen his understanding of this world.

Arjuna specifically expresses his desire to know (etad veditum icchāmi) about 6 subjects that come in 3 pairs (BG 13.1):

1. prakṛti [nature] and puruṣa [the enjoyer] (prakṛtiṁ puruṣaṁ caiva)
2. kṣetraṁ [the field] and kṣetra-jñaṁ [the knower of the field] (kṣetraṁ kṣetra-jñam eva ca)
3. jñānaṁ [the process of knowledge] and jñeyaṁ [the object of knowledge] (jñānaṁ jñeyaṁ ca)

Krishna first explains the second pair – the field (kṣetraṁ) and the knower of the field (kṣetra-jñaṁ). This (idaṁ) body (śarīraṁ) is called (ity abhidhīyate) the field (kṣetram), and one who knows this body (etad yo vetti taṁ) is called (prāhuḥ) the knower of the field (kṣetra-jña) by those who are learned (iti tad-vidaḥ). (BG 13.2)

And (ca), we should understand (viddhi) that Krishna (māṁ) is also (api) the knower (kṣetra-jñaṁ) in all fields (sarva-kṣetreṣu). This clearly brings out the fact that our position and Krishna’s position are constitutionally different, and therefore, the theory of unification of the individual knower (soul) and the super-knower (Supersoul) at any point in time is a myth – we are individual knowers of our fields (bodies) and Krishna is the ultimate knower of all fields (bodies). According to Krishna (mataṁ mama), the knowledge of the field and its knower (kṣetra-kṣetrajñayor jñānaṁ) is what is referred to as knowledge (yat taj jñānaṁ). (BG 13.3)

After unveiling the two knowers of the fields (or the bodies), Krishna goes on to summarize (tat samāsena me śṛṇu) the field itself (tat kṣetraṁ) – its constitution (yac ca yādṛk ca), transformation (yad-vikāri), and also (sa ca) its source (yataś ca yat), as well as (ca) who empowers it (yo yat-prabhāvaś). (BG 13.4) This is sung (gītaṁ) by various sages (ṛṣibhir bahudhā) in diverse varieties of Vedic hymns (chandobhir vividhaiḥ pṛthak). And, it is especially (caiva) concluded (viniścitaiḥ) in the Vedānta-sūtra (brahma-sūtra-padaiś) with rational cause and effect relationships (hetumadbhir). (BG 13.5)

The gross elements (mahā-bhūtāny), false ego (ahaṅkāro), intelligence (buddhir), the unmanifested (avyaktam), the eleven senses [10 senses + the mind] (indriyāṇi daśaikaṁ ca), the five sense objects (pañca cendriya-gocarāḥ), desire (dveṣaḥ), hatred (icchā), happiness (sukhaṁ), distress (duḥkhaṁ), the combination (saṅghātaś), consciousness (cetanā), and convictions or willpower (dhṛtiḥ) – this (etat), in summary (samāsena), is called (udāhṛtam) the field of activities (kṣetraṁ) along with its transformations (sa-vikāram). (BG 13.6-7)

In other words, the field of activities is constituted by 24 elements – 5 gross elements (earth, water, fire, air, and ether), 10 gross senses (5 knowledge-gathering senses – eyes, nostrils, ears, tongue, and skin, and 5 working senses – hands, legs, mouth, anus, and genitals), 5 sense objects (sight, smell, sound, taste, and touch), mind, intelligence, false ego, and the unmanifested mahat-tattva (the warehouse of material elements). The interaction of these 24 elements leads to the transformation of the field, which are summarized as desire, hatred, happiness, distress, their combination, consciousness, and willpower.