Genital vore involves devouring prey through a penis or vagina.  The latter route differs from unbirth because the prey is devoured, not merely engulfed.  While occasionally prey is passed on to the stomach after entering the body (anatomically impossible, but such inconveniences are often overlooked in fantasy roleplaying) and digested normally, more often prey devoured with a penis is sent down into the scrotum and usually transformed into sperm.  A character 'eaten' by a vagina will similarly become female lubricating fluid or simply be absorbed directly by the walls of the vagina or womb.

While vore is a sexual act, genital vore is an extremely direct, explicit example.  Whereas soft vore conquers prey by orally consuming and often digesting them, genital vore further humiliates and dominates prey by forcing them into private, regarded-as-somewhat-dirty organs.  The potentially 'noble' cause of nourishing a predator isn't often a factor in genital vore, as the prey becomes sexual fluids instead of life-sustaining nutrients.  The usual dominance/submission fetish applies, as do endosomatophilia, spermplay, macrophilia, microphilia, cock-worship, cunt-worship, wet-and-messy, and humiliation.

This is a common theme in Japanese media, featuring several examples of feminine monsters devouring males with their vaginas.  This plays into an ancient fear men have of the female genitals, fearing the 'insatiable opening' and even imagining vaginas with teeth.  It isn't a huge leap from regarding the vagina as receptive, to regarding it as hungry, even voracious.  Women who crave sex or who are possessive of their lovers may fantasize taking more than their lover's penis/fingers/tongue inside them.  Mere possession of a lover would be unbirth however, not genital vore.

[There are as of yet no authoritative publications from academics on the subject of vore as we know it, only on the loosely-related subject of cannibalism, so I rely on my identity as a vore fetishist for over a decade, author of many erotic vore stories, and frequent vore-scene roleplayer to lend authority to my definitions.]