The adjective confident describes when you feel certain – especially of a good outcome, like success. It can also describe a person who feels good about himself/herself.
A confidant or confidante is a person who can be trusted; a person to whom you often tell secrets or discuss personal issues.
When you tell a secret or private information to somebody, you are confiding in that person – telling the person things because you trust him/her to keep them secret.
Some confusion comes from the word confidence, which can be used in two ways:
1) As a noun for the quality of feeling good and strong about yourself:
Taking martial arts classes really helped boost my confidence!
His confidence grew as he practiced more.
2) Trust or faith in a person or thing:
– If someone tells you something in confidence or in strict confidence, it means they are trusting you to keep it a secret.
– If you place/put confidence in someone, it means you trust them.
– If someone betrays/breaks your confidence, it means they did something that destroyed the trust you had in them.