Pyramid showing the capitalist system, 1911. The inscriptions from top to bottom are: "We rule you", "We fool you", "We shoot at you", "We eat for you", and "We work for all" / "We feed all"
Class struggle, or class warfare or class conflict, is tension or antagonism in society. It is said to exist because different groups of people have different interests.
Looking at society this way is a feature of Marxism and socialism. Social sciences group people with similar social features into classes. Most of these features are economic.