In short, Brahman (or Paramātman) is the ultimate reality of the universe, the single binding unity behind diversity in all that exists[1]. Some people call it Brahman, others call it God and more scientifically inclined people call it reality.

There are many different definitions and interpretations of Brahman[2], both from a dualistic and nondualistic perspective. I understand Brahman in terms of the Advaita Vedanta school of thought, which holds a monistic view.

However, ultimately all descriptions of Brahman and distinctions between the various schools of thoughts are moot:

यस्यामतं तस्य मतं मतं यस्य न वेद सः ।

yasyāmataṃ tasya mataṃ mataṃ yasya na veda saḥ ।

अविज्ञातं विजानतां विज्ञातमविजानताम् ॥ ३ ॥

avijñātaṃ vijānatāṃ vijñātamavijānatām ॥ 3 ॥

Those by whom Brahman is not known, know it; those by whom it is known, know it not. It is not known by those who know it; it is known by those who do not know it.

Kena Upaniṣhad, 2.3.[3]

Notes

  1. Wikipedia: Brahman.
  2. Notably, the Yoga Sūtras of Patañjali, one of the foundational texts of classical Yoga philosophy, holds a dualistic view: the goal of yoga is not to join, but the opposite: to unjoin, that is, to disconnect puruṣa from prakṛti.- Edwin F. Bryant (2015).
  3. The Kena Upaniṣhad, translated by Vivekavani. Accessed at vivekavani.com, 2024-07-17.