The Jim Crow Laws were a set of laws that allowed and enforced segregation. For Example, there used to be a law that prohibited white people and colored people from getting married.
The social divisions in Maycomb are similar but differ from real live segregation because in Maycomb, there is a hierarchy that goes from Rich White People > Middle Class White People > Poor/Terrible White People > Black People. They're similar because Jim Crow Laws appear throughout the story in many ways.
Some connections to real-life racial themes are the injustices that fall upon the colored people in the book. An example of this is Tom Robinson who is found guilty dispite have a lack of evidence.