It is a personal characteristic, or protected class, which is generally not to be considered in area-related decision-making. If the basis was a motivating factor in the incident, then the incident is usually a discriminatory practice.
It is a decision or action, usually made by someone in authority, in one of the five areas, which adversely affects someone. "Failure to hire," "harassing conduct," "failure to accommodate," "unequal pay," and "termination" are considered incidents in employment. "Failure to serve" and "unequal service" are incidents in public accommodations.