There are actually two Walter Cunninghams, Jr. and Sr. They are a family of poor farmers that interact with the Finches.
We are first introduced to the Cunninghams on Scout’s first day of school, when the teacher asks Walter Cunningham Jr. where his lunch is. He has no lunch, and he cannot borrow a quarter because he can’t pay it back. He also has hookworms from not having shoes. Walter and his family do care, though, because his clothes are clean.
Scout informs Miss Caroline, the teacher, of the Cunningham tribe.
The Cunninghams never took anything they can't pay back- no church baskets and no scrip stamps. They never took anything off of anybody, they get along on what they have. They don't have much, but they get along on it. (ch 2)
Jem invites Walter for lunch, and Scout gets in trouble for yelling at him when he puts syrup on his food. Walter and Atticus talk like two adults.
Walter’s father has been one of Atticus’s clients, but he cannot pay in money because all the farmers are poor. As a result, he pays in farm goods. He is also well-respected in the community, as we can tell because he seems to be the leader of the mob that targets Tom Robinson in his jail cell.
At first, Mr. Cunningham is just one of the “sullen-looking, sleepy-eyed men who seemed unused to late hours” that confront Atticus. Yet Scout recognizes him, lectures him on entailments, and asks him to say hi to his son. She is confused when he does not enter the conversation because she does not realize what is happening.
I looked around and up at Mr. Cunningham, whose face was equally impassive. Then he did a peculiar thing. He squatted down and took me by both shoulders.
"I'll tell him you said hey, little lady," he said. (ch 15)
He then tells the mob to leave. Scout’s presence made him come to his senses and realize what he was doing. The others respected him, so they listened to him.