Arjuna , in the Bhagavad-Gita, was a Pandava Prince, going to war against the Kurus.
He was aided by Krishna who rode with him in his chariot.
The Kurus represent the lower animal urges of man. Arjuna who was also called Nara, man, thus represented a noble (Aryan means noble) man. Krishna riding with him in his vehicle represented the Atma, the Holy Spirit that guides each man and forms each man's own spirit.