Talented authors, such as Langston Hughes, go to great lengths to create realistic characters because they are central to a fictional plot moving forward. The more believable the characters are, the more a reader connects with the story. This means that when creating a character, the author imagines every detail about him including the way that a character speaks and the things he might say. In this way, the quotes of dialogue from a story exemplify that character's traits.
In "Thank You, M'am," for example, the reader immediately begins to understand the character of Mrs. Luella Bates Washington Jones from the following quotes.
"Was I bothering you when I turned that corner?...But you put yourself in contact with me. If you think that contact is not going to last a while, you got another thing coming."
Mrs. Jones said this right after she caught the young man who tried to rob her of her purse as she walked home late one night. Through these words the readers understands that Mrs. Jones is fearless and indignant. She means to teach the boy a lesson.
"I have done things too, which I would not tell you son, nor tell God if he didn't already know. So you sit down while I fix us something to eat."
Mrs. Jones says this to Roger after dragging him to her home immediately following the failed robbery attempt. With this quote, the author allows the reader to see that although Mrs. Jones is indignant, even angry about the attempted purse snatching, she is to some extent understanding and caring. Her words tell us she intends to feed the boy who just tried to rob her.
In these ways, through these quotes of her dialogue, author Hughes introduced us to Mrs. Jones' character.