The fundamentals theories of discrimination are simple.
It is illegal to discriminate against someone (applicant or employee) because of that person’s race, color, religion, sex (including pregnancy), national origin, age (40 or older), disability or genetic information. It is also illegal to retaliate against a person because he or she complained about discrimination, filed a charge of discrimination, or participated in an employment discrimination investigation or lawsuit.
The law forbids discrimination in every aspect of employment. Below is a short list of discrimination charges (of course there are several more).
Discriminating for a particular class is as unlawful as discriminating against a particular class. The primary theories of discrimination are based on Disparate Treatment and Disparate Impact.