Group vs Individual
For most people in an urban technological society, the single most important distinction that needs to be understood in depth is the group / individual dynamic.
All people (individuals) begin as part of a group. After birth they are part of a family and their individuality develops only to the extent that they leave the family. In a primitive society this involves a tremendous psychological process. But in a modern society there is often no real transition, and the result is that no true individual is formed.