A main character's confidant can be a best friend, kindly neighbor, grandparent, or business partner. This character listens to the hero as he ticks off reasons why he has to shoulder the blame and go on alone. The confident can supply information or try (unsuccessfully) to stop the headstrong hero.
A confidant offers advice even when it's not wanted. When the heroine proclaims she could never love that awful hero, the confidant helps the her talk though her feelings. The confidant always helps the heroine achieve her goal.
For a writer, a confidant is an ideal tool. With the interaction between a lead and his or her confidant, active dialogue replaces what otherwise could be long passages of introspection.
Donald Maas says, "The best kind of confidant is a character who is already part of the lead's life and would naturally play [the role of sounding board,] but who has reason to exist in her own right."