君子 (jūn zǐ, a man of virtue) was originally used to indicate a person's social status, generally referring to a ruler or a member of the aristocracy. Beginning with Confucius, the term acquired an additional moral dimension and came to mean someone of true virtue. The opposite of junzi is 小人 (xiǎo rén, a petty man).
In the Confucian tradition, 君子 is someone who is above a scholar and below a sage in terms of moral influence. A man of virtue pursues and practices the ideal known as Dao and regards Dao as the fundamental meaning of life above power or gains.
There is a saying in The Analects of Confucius: 君子喻于义，小人喻于利。(jūn zǐ yù yú yì, xiǎo rén yù yú lì) A man of virtue understands and observes what is morally right; while a petty man only has his eyes on and goes after what brings personal gains.