Short answers, pulled from the story.
Nirvana comes from the Sanskrit verbal root vā, meaning "to blow," combined with the preverb nis, meaning "out." The original meaning of the word is "blown out" or "extinguished." Scholars note that the Buddhists appear to have been the first to use the term in this soteriological sense.
Buddhist texts identify three fires, also called three poisons, that sustain the cycle of rebirth: raga (greed and sensuality), dvesha (aversion and hate), and avidya or moha (ignorance and delusion). Nirvana is the extinguishing of all three, forming the Third Truth on the cessation of dukkha in the Four Noble Truths.
The Buddhist scholastic tradition holds that the Buddha realized two types of nirvana. Sopadhishesa-nirvana, or nirvana with a remainder, came at his awakening while he still lived. Parinirvana, also called anupadhishesa-nirvana or nirvana without remainder, came at his death and is considered the final form.
Buddhism describes nirvana as stilling the mind and action unto emptiness, grounded in the doctrine of anatta (non-self), meaning no self exists in any being. Hindu nirvana in post-Buddhist texts is also a stilling of the mind but is not emptiness; it is described as infiniteness and the union of Atman (the true self) with Brahman (the universal absolute). Mahatma Gandhi stated that the Buddhist nirvana is shunyata (emptiness) while the nirvana of the Bhagavad Gita means peace, expressed as brahma-nirvana.
Brahma-nirvana appears in verses 2.72 and 5.24-26 of the Bhagavad Gita. It describes the state of release and union with Brahman. Scholars including Zaehner have argued the term was adopted from Buddhism and used in the Gita for the first time in Hindu literature.
In Jainism, nirvana represents the release of a soul from karmic bondage and the cycle of existence, and it is used interchangeably with moksa in Jain texts. The Uttaradhyana Sutra describes it as a place where there is no old age, death, pain, or disease, calling it freedom from pain and perfection. Hermann Jacobi published this translation in 1895.