Maycomb in the novel acts as a kind of microcosm of the rest of the world. Differences in social status is one of the key themes of the novel, and we see that Maycomb has a highly complicated and elaborate social heirarchy or pecking order, which is presented to us through the eyes of the children, who are constantly baffled by it. This social heirarchy dictates behaviour, who you can talk to and how, and who you can spend time with.
At the top of this heirarchy are the Finches, with most of the townspeople beneath them. Country farmers who are quite simple minded, such as the Cunninghams, lie below the townspeople, with an even lower layer reserved for the "white trash", such as the Ewells. However, crucially, the large black community, despite its many good qualities, is shown to dwell even below the Ewells, which means that Bob Ewell is able to persecute Tom Robinson out of a sense of his own lack of importance.
Inequality then is shown in this novel, but not just racial inequality. Inequality as a whole is shown to be irrational and destructive, and is critiqued through the eyes of the children. For example, Scout is unable to understand why Aunt Alexandra will not let her play with Walter Cunningham. The children's confusion at these rigid social heirarchies is used to critique the importance of social rigidity in the world at large and also prejudice in the way we interact with one another.