The modern use of the term was popularized by Peggy McIntosh's 1988 paper on white and male privilege, later excerpted as "White Privilege: Unpacking the Invisible Knapsack." She listed everyday advantages she had as a white woman, such as being able to shop without being followed. The idea has older roots. In 1935, W.E.B. Du Bois described a "public and psychological wage" paid to white workers in the form of status and access.
Privilege is usually invisible to those who have it, because it feels like the normal way the world works. People can hold privilege in one area and face oppression in another, which is a key insight of intersectionality. A white woman may face sexism while benefiting from racial privilege.
Critics argue the concept can produce guilt without change, or be heard as an accusation. ARD's approach is that privilege is a fact about systems, not a moral judgment about individuals. The point of naming it is to use the access it brings to change those systems.