Bhagavad Gita Chapter 13, Verse 6

महाभूतान्यहंकारो बुद्धिरव्यक्तमेव च | इन्द्रियाणि दशैकं च पञ्च चेन्द्रियगोचराः ||

mahā-bhūtāni ahaṅkāro buddhir avyaktam eva ca indriyāṇi daśaikaṁ ca pañca cendriya-gocarāḥ

The field consists of the five great elements, ego, intellect, the unmanifest, the ten senses, and the five objects of the senses.

Krishna begins listing what constitutes the field. The five great elements (earth, water, fire, air, space) form the physical body. Ego (ahaṅkāra) is the sense of 'I' that identifies with the body. Intellect (buddhi) is the faculty of discrimination. The unmanifest (avyakta) is the source from which everything arises. The ten senses (five of perception, five of action) are your means of experiencing the world. The five objects of the senses are what you perceive. All of this—your entire experience—is the field. Most people think they are these things. But you're not. You're the knower who experiences them. This list helps you recognize everything that's part of the field, so you can distinguish it from the knower.