Choi was a man who visited Neo at his apartment to pick up an illegal software that could clear parking tickets that Neo had written in his spare time to make extra money.
When Choi receives the disks, he says to Neo, "Hallejuah, man. You're my savior, man. My own personal Jesus Christ." This line is an allusion to Neo's ultimate destiny as The One.
Choi is accompanied by Dujour. Together, the two characters' names form choi du'jour, or, in rough French, "Choice of the Day", an allusion to the power of choice within the Matrix and the choices that Neo makes that lead him to his destiny.