Demographic criteria define a group of persons for whom the algorithms have identified a common socio-demographic characteristic. Facebook collects data which appear in the declarative part as well as geolocalization data of member profiles and can consequently establish relevant socio-demographic connections. Some examples of behavior criteria: work employer, job title, Industries, parental status, relationship status, educational level, etc.
(For more information: https://www.facebook.com/business/ads/ad-targeting )