Short answers, pulled from the story.
The Sanskrit word Brahman derives from the root brih, meaning to swell, expand, grow, or enlarge. This neuter noun stands apart from the masculine Brahma and refers to an unchanging Ultimate Reality in Hinduism.
Brahman appears in hundreds of hymns across the Rigveda and Atharvaveda dating to the late second millennium BCE. Early usage implied power immanent in sound, words, verses, and formulas of the Vedas before evolving into a metaphysical principle.
The Brihadaranyaka Upanishad 1.4.10 declares I am Brahman while Chandogya Upanishad 3.14.1 states All this is Brahman. The Śāndilya doctrine asserts that Atman exists inside man and is identical with Brahman.
Advaita Vedanta espouses nondualism where Brahman remains the sole unchanging reality across space and time. Adi Shankara argued knowledge of Brahman cannot be obtained except through self-inquiry removing ignorance Avidya.
Buddhism rejects the Upanishadic doctrine of permanent Self or cosmic counterpart Brahman through its Anatta doctrine. Damien Keown states Buddha found no evidence for existence of either personal Self or its cosmic counterpart.