This article is about the general phenomena of Class warfare. See Class War for information about the newspaper/organisation of that name.
In capitalism there are wage workers (proletariat) and capitalists. Wage workers do not own or have control over the means of production, and subsist by selling their labor power to capitalists. Capitalists own and control the means of production, and subsist by expropriating surplus labor value from the wealth-creating workers.
In a Marxist-Leninist dictatorship of the proletariat the leaders of the ruling party, the new class control the means of production, although unlike capitalism, they do not extract profit from it. Some communists like followers of Trotsky or Mao say the solution to this is permanent revolution, while some critics like anarchists say the solution is that factories and offices be run by the workers who work in them.
Thus a socio-political imbalance exists between individuals of extreme wealth or power and those with little or no wealth. The interests of those in whom power is established will often dramatically conflict with the interests and needs of classes without power.
Furthermore, since the mechanisms by which wealthy or powerful persons will increase or maintain their financial status and power are related and similar to another, they tend to develop similar political needs, and act in concert as a political group to those ends.
This is of course, is in direct contradiction to the wants, and often needs, of the greater majority. The only means by which people have in modern times made progress against this imbalance has been through democracy, and the institutionalized respect and protection of personal liberties.
Fundamentally, there is little difference between the class warfare that existed between the Victorian era monarchy and the common public, and a modern corporation and its workers, who may own part or most of the corporation.
-- Unionss are a modern incarnation of public will in class warfare. Representing a political group of like minded working people, unions have revolutionised health and safety standards in industrial economies. Corporations are companies that exist as perpetual entities. Their function is as a vehicle for business enterprise, while transcending the bounds of mortality and liability that accompany an individual-owned enterprise.