Short answers, pulled from the story.
In Buddhism, enlightenment is the Western translation of Sanskrit bodhi, from the root budh meaning "to awaken" or "to recover consciousness". It also translates terms such as vimutti (freedom from fetters), nirvana (the blowing out of disturbing emotions), and prajna (insight or wisdom). The term was popularized in English through 19th-century translations by British philologist Max Müller.
British philologist Max Müller is credited with popularizing the term. The first recorded use of "enlightenment" in this sense is credited by the Oxford English Dictionary to the Journal of the Asiatic Society of Bengal in February 1836. By the end of the 1880s, the terms "enlightened" and "enlightenment" dominated English-language writing on Buddhism.
In early Buddhism and Theravada, bodhi and nirvana are synonymous: both refer to freedom from greed, hate, and delusion and the cessation of suffering. In Mahayana thought, bodhi is specifically the realization of the inseparability of samsara and nirvana, and the unity of subject and object, while nirvana retains the meaning of the extinction of disturbing passions.
Buddhist tradition recognizes three types: Arhats, who reach Nirvana by following the Buddha's teachings; Pratyekabuddhas, who achieve Nirvana through self-realization without teachers and do not teach the Dharma; and Samyaksambuddhas, who reach Nirvana through their own effort and wisdom and teach it to others. Siddhartha Gautama is the exemplar of the third type, his attainment described as anuttara-samyak-sambodhi, or highest perfect awakening.
Both kensho and satori are Japanese terms used in Zen traditions. Kensho means "seeing into one's true nature", with ken meaning "seeing" and sho meaning "nature" or "essence". Satori refers to the experience of kensho rather than the seeing itself, and the two terms are often used interchangeably. The Rinzai tradition regards kensho as essential to Buddhahood but holds that further practice is still required.
Bodhi Day, marking Sakyamuni's enlightenment, is observed on different dates across the Buddhist world. In Sri Lanka, it is celebrated at Vesakha Puja, the full moon in May, known as Sambuddhatva jayanthi. Japan observes a secular Bodhi Day on the 8th of December. China, South Korea, and Vietnam mark it on the eighth day of the 12th lunar month.