Short answers, pulled from the story.
Nirvana means blowing out a flame or quenching an activity of the grasping mind. It represents the cessation of suffering, craving, and rebirth within samsara. The term connects to escaping the forest of defilements or stopping the weaving of life after life.
Early Buddhist sources from the time of the Buddha describe nirvana as the extinction of passion, hatred, and delusion. This state involves the cessation of all feelings which are rejoiced in when the break-up of the body occurs. Later Theravada Abhidhamma texts like Vibhanga define it as unconditioned element existing since ancient times.
Paul Williams notes at least two conflicting models on bodhisattva attitude toward nirvana in Mahayana tradition. Etienne Lamotte analyzed the Mahāprajñāpāramitopadeśa supporting ideas about entering complete nirvana. Asanga fourth century CE developed the theory of apratiśthita non-abiding highest nirvana through Yogacara school.
Alternative idea Mahayana nirvana appears in Tathagatagarbha sutras title meaning garba womb matrix seed containing Tathagata Buddha. These sutras suggest all sentient beings contain Tathagata essence core essential inner nature. Doctrine appeared probably later part third century CE with verifiable Chinese translations first millennium CE.
Modern academic debates examine whether nirvana state mind place mere absence existence or positive reality immortal state similar godly abode svarga found Edicts Ashoka. Stanislaw Schayer argued 1930s Nikayas preserve elements archaic form Buddhism close Brahmanical beliefs survived Mahayana tradition. Alexander Wynne holds no evidence Sutta Pitaka Buddha held view best shows some early Buddhists influenced Brahminic peers.