What role do minor characters play in a piece of literature?

Answer 1

Minor characters are basically color - they provide interactions with the main characters and cause things to happen that are needed, but their role can be played by any minor character, so they're pretty much interchangeable.

Answer 2

Minor characters serve many functions. They may provide information the main characters need. They may provide background color and setting. They may assist the main characters. They may even provide comic relief.