Short answers, pulled from the story.
George Lucas created the character Qui-Gon Jinn for the 1999 film The Phantom Menace. He originally envisioned an American actor in the role but ultimately cast the Northern Irish actor Liam Neeson.
Qui-Gon Jinn's name is derived from the Chinese word qigong and the Arabic word jinn. The full name can be translated as Guardian Spirit of the Living Force.
The 2005 film Revenge of the Sith reveals that Qui-Gon learned how to become a Force spirit after death. This ability allows him to retain consciousness even after his physical body perishes.
During a ferocious lightsaber battle Darth Maul fatally wounds Qui-Gon. After defeating Maul Obi-Wan promises to train Anakin for Qui-Gon before he dies.
He takes note of Obi-Wan's skills but refuses to train him due to his uncontrolled anger. During the encounter with Xanatos Qui-Gon realizes Obi-Wan's potential and accepts him as his Padawan.