BDSM is an acronym, generally accepted as standing for Bondage, Discipline, Sadism and Masochism, although the DS can also be taken as Dominance and Submission. It is a set of practices or kinks that can involve being tied, sensory deprivation, spanking, whipping or other forms of pain, mostly with the aim of sexual arousal.
There are many fallacies around BDSM, for example the idea that submissives are weak or that it is natural for men to be dominants and women submissives. Each person in the lifestyle finds a mix of practices and a person or people who suit their needs and wants.
Story of O, the title of the English edition, is an account of a French fashion photographer, known only as O, who descends into debasement, torment, humiliation, violence, and bondage, all in the name of devotion to her lover, René. Over the course of the novel she is blindfolded, chained, flogged, pierced, branded, and more. The first chapters of the book cover the time she spends being trained in a chateau at Roissy just outside Paris.
The book was originally published in France in the 1950s and is set around Paris, probably just after the Second World War. It was written by a French woman, originally known by the pseudonym Pauline Reage, later revealed as Dominique Aury, itself a name adopted in her thirties by Anne Desclos. A number of films have been made, the best known being from 1975, directed by Just Jaekin and starring Corrine Clery.