This porn video tag refers to a specific type of content featuring transgender or shemale individuals. "Shemale" is an outdated term used for describing individuals with male genitals and female secondary sexual characteristics. In this context, "self-fuck" means that the individual is engaging in autoerotic activities involving their own body, primarily focusing on their male and female genitalia.
So, this tag indicates a video where a transgender or shemale person is pleasuring themselves through self-stimulation and masturbation, involving both their penis and vagina. This type of content can be enjoyed by those who appreciate the unique blend of masculine and feminine elements in the performer's body, as well as those who are into autoretic activities and self-pleasure.