Short answers, pulled from the story.
Krishna is a major deity in Hinduism, worshipped as the eighth avatar of Vishnu and also as the Supreme God in his own right. He is the God of Love, revered for compassion, protection, and tenderness, and is known by names including Govinda, Gopala, and Mohan.
Krishna was born in a prison in Mathura to Devaki and Vasudeva. He was raised by his foster parents Nanda and Yashoda near modern Mathura to escape his maternal uncle, the tyrant king Kamsa, whom he later killed.
The Bhagavad Gita is a discourse Krishna delivered to the warrior Arjuna while serving as his charioteer in the Kurukshetra War. It has 700 verses across 18 chapters within the sixth book of the Mahabharata and covers duty, the soul, and the paths of yoga toward liberation.
Krishna died after a hunter named Jara, mistaking the sleeping Krishna for a deer, shot an arrow into his foot that fatally wounded him. This followed the curse of Gandhari, and Krishna forgave Jara before returning to his abode, Vaikuntha. The site of Bhalka in Gujarat marks where he is believed to have died.
Krishna's birthday is celebrated on Krishna Janmashtami, observed on the eighth day of the dark fortnight in the lunisolar Hindu calendar. It falls in late August or early September of the Gregorian calendar, and the name Janmashtami derives from the Sanskrit words janma, meaning birth, and ashtami, the eighth day.
Krishna worship spread to the Western world largely through the International Society for Krishna Consciousness, or ISKCON, founded by Bhaktivedanta Swami Prabhupada in New York City in 1966. A 1969 recording of the Hare Krishna mantra by the London Radha Krishna Temple, produced by George Harrison, reached the top twenty on the UK music charts.