The term ruling class refers to the social class of a given society that decides upon and sets that society's political policy by mandating that there is one such particular class in the given society, and then appointing itself as that class.
Sometimes, there is a ruling class in a particular sector of the upper class that adheres to quite specific circumstances: it has both the most material wealth and the most widespread influence over all the other classes, and it chooses to actively exercise that power to shape the direction of a locality, a country, and/or the world.
A sociologist, C. Wright Mills, argued that the ruling class differs from the power elite. The latter simply refers to the small group of people with the most political power. Many of them are politicians, hired political managers, and military leaders.
Under the Marxist view of capitalism, the ruling class, the capitalists or bourgeoisie, consists of those who own and control the means of production and thus are able to dominate and exploit the working class, getting them to labor enough to produce surplus-value, the basis for profits, interest, and rent (property income). This property income can be used to accumulate more power, to extend class domination further. The economic power of such a class gives it extraordinary political power, so that state or government policies almost always reflect the perceived interests of that class.
Ruling classes tend to be looked at negatively because they are often viewed as having little respect of or interest in the rights of perceived "inferior" classes.
Analogous to the class of the major capitalists, other modes of production give rise to different ruling classes: under feudalism, it was the feudal lords, while under slavery, it was the slave-owners. Under the feudal society, feudal lords had power over the vassals because of their control of the fiefs. This gave them political and military power over the people. In slavery, because complete rights of the person's life belonged to the slave owner, they could and did every implementation that would help the production in the farm.
Mattei Dogan, in his recent studies on elites in contemporary societies, has argued that because of their complexity and their heterogeneity and particularly because of the social division of work and the multiple levels of stratification, there is not, or can not be, a coherent ruling class, even if in the past there were solid examples of ruling classes, like in the Russian and Ottoman Empires, and the more recent totalitarian regimes of the 20th century (communist and fascist).
There are several examples of ruling class systems in movies, novels, and television shows. The 2005 American independent film The American Ruling Class written by former Harper's Magazine editor Lewis Lapham and directed by John Kirby is a semi-documentary that examines how the American economy is structured and for whom. Although it is a US film, the same principles also apply to many other countries as well.
In the novel Brave New World, by Aldous Huxley, everyone is genetically made and classified. The Alpha class is the ruling class because they have the highest positions possible and control most of the world in the novel. This situation can also be found in the George Orwell novel Nineteen Eighty-Four where Big Brother and the government literally control what the nation hears, sees, and learns.
Examples in movies include Gattaca where the genetically-born were superior and the ruling class and V for Vendetta, which had a severe totalitarian government in Britain. The comedic film The Ruling Class was a satire of British aristocracy, depiciting nobility as self-serving and cruel, juxtaposed against an insane relative who believes that he is Jesus Christ, whom they identify as a "bloody Bolshevik".