The type of character to whom secrets or private matters are disclosed, often called the "trusted friend," is known as a confidant (or confidante if female).

Explanation:

• A confidant is a character in literature or drama who is entrusted with private information by another character.
• This role allows the main character to reveal inner thoughts, feelings, or plans, helping to develop the plot or provide insight into the protagonist's mind.
• The confidant often serves as a sounding board and can be crucial for character development.

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