Reference groups refer to

the relatively permanent, homogeneous divisions in a society that consists of people who share similar values, interests, and behaviors.

individuals who exert direct or indirect social influence over others.

one or more persons whom an individual uses as a basis for comparison regarding beliefs, feelings, and behaviors.

those buyers who, through the size of their purchases, affect where marketing dollars will be spent.

those with whom a person does not wish to be a member of or identified with.