Overview
A daddy in gay culture is a slang term meaning an (typically) older man sexually involved in a relationship or wanting sex with a younger male. The age gap and maturity gap is key to the relationship.
The term has increasingly been applied to heterosexual relationships. In addition to being older and/or more experienced, it can sometimes have connotations of submission.
In the homonormative sense, a dad (or daddy) is a gay man who applies a state of mind that encompasses care, consideration, mentorship and leadership to a gay junior male. A dad is usually a cis-gendered male, but this may not always be the case. The dad has the welfare of a younger man at heart, and his natural impulse is benevolent guardianship.
In the heteronormative sense, the father/son, teacher/student, coach/protégé relationship is assumed to be finite and not questioned, but an ongoing relationship is looked at askance. Dad–son relationships are a form of mentoring, and the shared homosexuality of the partners is a personal extension of societal gender norms and expectations about masculinities. Most partners in dad–son relationships subscribe to common values: masculinity is praised and therefore celebrated between them. It has become a stereotype in the gay community.
From Wikipedia (CC BY-SA 4.0).