Disparate treatment means “different treatment.” Disparate treatment is illegal when it is aimed at an employee or independent contractor because of their membership in a protected class.
Most often, illegal disparate treatment results in an employee not getting a raise, being passed over for a promotion, being assigned an undesirable shift or job duties, or being fired because of a characteristic they have which belongs to a protected class. For example, being male or female is a characteristic of the protected class gender; being Muslim, Catholic, Jewish, or Hindu is a characteristic of the protected class religion.
See, CACI 2500 and Government Code, § 12940.