Japanese animated porn. Features creepy teenage girls with gigantic boobs who scream "NO NO PLEASE STOP" while gravelly-voiced men or aliens rape them in every orifice and then stuff ball-gags and fetish toys into their throats. 90% of hentai females are virgins, unless they are over the age of 20. If they are they will usually apologize for being so old and having sexual partners prior to screwing the man.
There is a gentler form of hentai which is aimed at an even more creepy audience of male virgins and ephebophiles. This usually features a girl in her mid-teens who is having sex with her boyfriend or an older man for the first time. The girl will make remarks about how exciting the penis is and how fascinating it is that she is allowed to jam it into her tiny mouth. When the guy mounts her, she'll scream in pain.
Hentai is enjoyed by people of all ages and walks of life who have never had sex, never have sex or have forgotten what sex is like.
A: Dude, check out this awesome hentai where the girl gets five alien penises stuck down her throat and then vomits blood and dies!
B: I'd rather watch some regular porn, thank you