Background details play a crucial role in enhancing the realism of a series by creating a more immersive and believable world for the viewers. These details can include elements such as set design, props, costumes, and even minor characters. They provide context, depth, and authenticity to the overall narrative, making the series more engaging and relatable to the audience. By paying attention to these subtle nuances, the creators can transport viewers into the world they have crafted, ultimately enhancing the viewing experience and making the series feel more realistic.