Realism is defined by the eNotes/Wikipedia page as “a style that depicts the actuality of what the eyes can see.” This refers to technique and style, as well as subject matter.
The realist painters and photographers of the 19th century were only interested in capturing scenes from everyday, real life. These realists were not interested in painting things from the past, from imagination, or from exotic places. They were only interested in what was real and present in their world.
Realism was preceded by and was a response to the movement called Romanticism. Romantic artists painted scenes that were wildly different from real life. They used dramatic colors to portray emotionally charged events from history, literature, and myth.
An example of Romantic painting is The Raft of the Medusa by Théodore Géricault. In this painting a small makeshift raft is depicted cluttered with the bodies of survivors of the French ship La Méduse. Some of the rafters are alive and wildly trying to signal a ship in the distance, while others are either dead or just on the verge of death. Waves are splashing, and people are crying out. It really could not be more dramatic.
The realists were totally against this type of art. They felt it was the artist’s job to depict the truth of real life, not to indulge wild fantasies.