The Ewells are a poor family that live in Maycomb. Bob Ewell is the father and he is described as a drunk and a poor father and citizen. The people pity him and allow him and his family to do things that they would not permit others to do. This is because of their horrible situation. Enforcing the law on them would make their situation worse, because Bob and his family are so dysfunctional.
Atticus tries to explain this to Scout. He writes:
“Let us leave it at this,” said Atticus dryly. “You, Miss Scout Finch, are of the common folk. You must obey the law.” He said that the Ewells were members of an exclusive society made up of Ewells. In certain circumstances the common folk judiciously allowed them certain privileges by the simple method of becoming blind to some of the Ewells’ activities. They didn’t have to go to school, for one thing. Another thing, Mr. Bob Ewell, Burris’s father, was permitted to hunt and trap out of season.
“Atticus, that’s bad,” I said. In Maycomb County, hunting out of season was a misdemeanor at law, a capital felony in the eyes of the populace.
“It’s against the law, all right,” said my father, “and it’s certainly bad, but when a man spends his relief checks on green whiskey his children have a way of crying from hunger pains. I don’t know of any landowner around here who begrudges those children any game their father can hit.”
I know that this is a lengthy quote, but it is essential to know how Atticus views the Ewells. In a broken world, sometimes you have to bend the rules.
Finally, the the court case that takes center stage in the book concerns the Ewells. Bob's daughter Mayella accuses Tom Robinson of raping her, when the one who beat her was her father.
Here is a clip from the movie where Bob Ewell confronts Atticus, highlighting the differences between their characters: