"Gay casting" is a term used to describe a particular type of adult film where young men are auditioned for roles in gay pornographic movies. These auditions typically involve nudity, masturbation, and/or sexual activity between the participant and another person or object.
In this context, "gay" refers to the sexual orientation of the participants involved - that is, they are men engaging in sexual activities with other men. The casting process usually involves several candidates who perform intimate acts to prove their skills and suitability for the role.
This tag would be associated with videos that depict the auditioning and casting process for gay pornographic films. Viewers who enjoy this type of content may find it exciting or intriguing to watch young men try out for roles in an industry where sexual activity is a key component of the job.