Discrimination occurs when an employer takes an adverse action action against an employee, the employee's "protected status" was a substantial motivating reason for the adverse action, the employee is harmed, and the adverse action was a substantial factor in causing the employee's harm. (Cal. Gov't Code section 12940 et seq., CACI Jury Instruction 2500).
Protected statuses include: race, national origin, ethnicity, gender/sex, age (over 40 years old), disability, medical condition, marital status, sexual orientation, and religion. (Cal. Gov't Code section 12940 et seq.)
An example of race discrimination can be: a supervisor making racial epithets about the race of a certain employee, giving the employee a poor performance evaluation rating despite the employee's satisfactory performance, giving employees of the a different race than the employee better performance evaluation ratings despite their poor performance, and the supervisor firing the employee because of his race.