Adetail in a piece of writing which is of some interest to the reader, but is not central or important to the subject matter is called a detail.

In writing, a detail is meant to provide facts, information, or description about a particular person, place, or thing. They help not only provide more information but also to bring something to life in the reader's mind. Details in writing can be "major" or "minor."

A major detail would have clear importance to the subject matter. For example, when writing a summary of a novel, major details would include the setting, main characters, and important events.

Minor details, on the other hand, may be interesting to readers, but these details are not significant to understanding the subject matter. For example, when writing a summary of a novel, a minor detail might include mentioning a minor character who appears only once and does not impact the plot of the novel. 

To give another example, if someone is writing a review of a movie, major details would include the names of the actors in it. Another major detail might be the name of the director. Important plot points, including the movie's genre, are also major details. Minor details about the movie might include the movie's budget. Another minor detail might be the name of the studio that produced the film. Finally, another minor detail might be the city in which it was filmed. None of these minor points are central to understanding whether or not you want to go see the movie in theaters.

Therefore, the answer to the above question is "minor." A detail in a piece of writing which is of some interest to the subject but is not central or important to the subject matter is called a MINOR detail.

She is persuading him to do better