If you're confident you are sure about something, someone, or yourself. He was confident he could keep his balance and cross the river on the skinny log, but he wasn't so confident that the log was strong enough to hold him.
Confident is often a word of assurance. Someone may ask, "Are you sure that's the right way to do it?" and then, just to be assured, they might say, "So, you're confident that's the right wire to cut so the bomb doesn't blow?" Being really sure of something or being sure of yourself is being confident. "He held his head high, but not in an arrogant or show-off way; he was just confident about who he was. He liked himself."