It's subjective and depends on the story, but typically minor characters or extras have less importance than main characters. These characters usually have limited impact on the plot and development of the story.
Background Characters
Flat Character
Each important character in a story moves the story forward.
A flat character is a type of character that exhibits only one or two qualities or traits and is less important to the story. Flat characters are often used to provide background or contrast to main characters and to help advance the plot.
In my opinion Sita is the most important character in Ramayana.
Perhaps you mean to ask about a subplot? A subplot is a less important second plot in a literary work or film. Perhaps it is a story that has been written by a character of the story, although this is unlikely.
I discussed this with my teacher in English class and she agreed withe me the there is 2 types of conflict in the short story, "The First Seven years". Character v.s. Character and one that is relevant but less important is Character v.s. society
Background Characters
The main character will be the person that the story is about, either the hero or the villain. Your teacher wants you to think about the story and decide which character is the most important to the story.
character- driven
A static character is a character who has remained unchanged throughout the entire story. Obviously, this is less common on fiction because usually when something happens to a character it alters their personality of outlook on life in some way. Most times a static character is a side character, because he/she wouldn't be important enough to go through a change in the story - that's easily left out. If a character has changed in the story, though, we call that a dynamic character.
The most important being in your story is the main character -- it doesn't have to be a human!
Secondary Character