PORNOGRAPHY is a daydream in which activities, usually but not necessarily overtly sexual, are projected into written or pictorial material to induce genital excitement in an observer. No depiction is pornographic until an observer's fantasies are added; nothing per se is pornographic. There is always a victim, no matter how disguised: no victim, no pornography. The use of such matter is an act of perversion with several components. (Perversion is defined for the present purpose as indefinitely repeating conscious preference for a genitally stimulating exciting act which is not genital heterosexual intercourse.) The most apparent is voyeurism. The second, hidden (unless the person is an overt sexual sadist), is sadism; sadism is, however, rather easily demonstrated. The third, more hidden (unless the person is an overt sexual masochist), is masochism; masochism is hard to demonstrate, since it is hidden in an unconscious identification with the depicted victim.
These above components
Stoller RJ. Pornography and Perversion. Arch Gen Psychiatry. 1970;22(6):490-499. doi:10.1001/archpsyc.1970.01740300010002