Short answers, pulled from the story.
The Realist movement in France began in the aftermath of the French Revolution of 1848 and was led by the painter Gustave Courbet. Courbet rejected the polished academic style to depict the world as it actually existed, including its mud, poverty, and ugliness. This movement marked a radical shift from painting gods and heroes to painting dead cows and funeral processions.
Naturalism was a term adopted in the 19th century by artists who sought to distinguish themselves from political Realists by adopting a quasi-scientific approach. The originator of the term was the French art critic Jules-Antoine Castagnary, who in 1863 announced that the naturalist school declared that art was the expression of life under all phases. Naturalist painters used tighter brushwork and avoided politics to focus on the accurate depiction of the physical world.
Key figures in the Realist movement included Gustave Courbet, Jean-François Millet, and Honoré Daumier. These artists turned their eyes away from the aristocracy to find beauty and truth in the lives of peasants, laborers, and the working class. They painted subjects such as dead cows, funeral processions, and the harsh realities of everyday life without the filter of romantic imagination.
Realism influenced theater through playwrights like Anton Chekhov who used camera works to reproduce an uninflected slice of life. In literature, writers such as Émile Zola, Gustave Flaubert, and Henrik Ibsen brought naturalism into novels to depict true-to-life drama. Cinema was influenced by Italian Neorealists like Vittorio De Sica and Roberto Rossellini who used location shooting and non-professional actors to create authenticity.
Ancient traditions such as the verism of the Roman Republic and the illusionism of the Greek painter Zeuxis influenced the development of Realism. The sculptor Demetrius of Alopece in the 4th century BCE preferred realism over ideal beauty, and Roman politicians demanded truthful portraits even if subjects were ugly. The Early Netherlandish painters of the 15th century, such as Jan van Eyck and Robert Campin, also developed techniques that allowed for the accurate depiction of the physical world.