Erotic humiliation of a woman is performed at Wave-Gotik-Treffen music festival, Germany, 2014.
She is stripped naked, hung upside down, whipped and a master doing roleplay of a devil forces himself on her.
It can also be for a set period of time (a "scene") or an ongoing facet of a relationship.
Humiliation is a subjective issue, and is dependent on context.
Humiliation in general stimulates the same brain regions that are associated with physical pain, the inference being that humans evolved to remember social rewards and punishments as strongly as they recall physical reward or pain in response to their environment.
As with any form of pain experimentation in a sexual context, consent and (paradoxically) a high degree of awareness and communication are needed to ensure that the result is desirable, rather than abusive.
Some humiliation roleplay (pup-play and age play in particular) is combined with loyalty and care-giving to the extent that these fetishes can be seen as exercises in trust rather than primarily a humiliation fetish.
The desire to be beneath the other partner during intercourse, the idea of "getting caught" (as in having sex in the garden or woods), and simulated rape are emotional games that emphasise status, vulnerability, and control.