The term Ingsoc is used in George Orwell's novel 1984. It was invented in the novel as one of the many neologisms that comprise "Newspeak," an artificial form of language associated with "doublethink" and designed to brainwash the public. It is not used outside this novel.
Within the framework of the novel, Ingsoc originally stood for "English socialism" but has come to mean the current social and political form of organization in Oceania. The basic structure of this society is sometimes also described as "Oligarchical Collectivism," in which the economy is state-controlled and collectivist but is run by an oligarchy (a small group of people) as opposed to democratic socialism where power is more broadly distributed.
The society is sometimes portrayed as a pyramid with "Big Brother" at the apex, followed by a small number of people belonging to the "Inner Party," a slightly larger group belonging to the "Outer Party," and finally at the bottom of the class hierarchy the masses or "proles" who are basically powerless and do various forms of menial labor.