The porn video tag "gay sex" indicates that the content features homosexual activity between men. In this context, "gay" refers to the sexual orientation of the participants and is used as a descriptor for the type of pornography being viewed or discussed. It signifies that the video displays intimate acts between two or more males, which may include but are not limited to oral sex, anal sex, and other forms of physical intimacy. This tag helps viewers find content that specifically caters to their sexual preferences.