What does Jem mean when he tries to explain to Scout the "four kinds of folk"?

In actuality, Jem is explained the social hierarchy of Maycomb, as well as the conflicts between them.

There’s four kinds of folks in the world. There’s the ordinary kind like us and the neighbors, there’s the kind like the Cunninghams out in the woods, the kind like the Ewells down at the dump, and the Negroes.”

“What about the Chinese, and the Cajuns down yonder in Baldwin County?”

“I mean in Maycomb County. The thing about it is, our kind of folks don’t like the Cunninghams, the Cunninghams don’t like the Ewells, and the Ewells hate and despise the colored folks.”