Realism depicts the world, its events, and people as they really are. There is no personification of people as mythological beings, no one is glorified, romanticizing anyone or anything is out. Realism is a social commentary on the world in which we live. Artists took the common and ordinary, and elevated them to a higher status.
The focus of Realism is on the common man. For too long the workers, peasants, and laborers of life were never the subject of art. Why? For one thing, common people never had the money to commission works of art. No farmer could trade crops for a portrait of himself farming, for instance. Nor did common people have the money to go to museums, Salons, or Academies of Art. And this despite making up the vast majority of people on Earth.
Artists like Gustave Courbet felt the need to depict ordinary people and show the rest of society what their lives were like. It was social commentary, pure and simple.