Made popular by the adult film industry, this is a technique performed during fellatio where the partner's penis is inserted deep into the mouth and throat, far past the gag-reflex. Since we all know that the best blow jobs make use of the lips and tongue, deep throating doesn't actually make oral sex better, it is more of a parlor trick. If you choose to practice though, make sure you have an empty stomach since triggering the gag reflex can induce vomiting.