Question

Quick & easy!!!!
Read this excerpt from "The Diamond Necklace":

"The girl was one of those pretty and charming young creatures who sometimes are born, as if by a slip of fate, into a family of clerks. She had no dowry, no expectations, no way of being known, understood, loved, married by any rich and distinguished man; so she let herself be married to a little clerk of the Ministry of Public Instruction."

What is the benefit of beginning a narrative with a description of a key character?