Truth is an accurate representation of reality.
Truth is accepting honesty as an absolute moral good, rejecting relativism.
Truth can also refer to personal integrity, wisdom and good conscience - the stereotypical "honest man" who can be trusted in business dealings.
Truth is most highly valued when it harms the teller; for example, admitting one's error to the boss at work, even when there is no possibility of her finding out on her own that you made the mistake.