自信 (zì xìn) is 'self-confidence' — a belief in your own abilities. It differs from 信心 (xìn xīn), which is confidence in someone or something else, and from 信任 (xìn rèn), which means 'to trust' another person. Unlike 自满 (zì mǎn, 'complacent'), 自信 is a positive trait without the negative sense of being overly satisfied.