Ralph Ellison presents the concept of racism through its effects on a Black man, his four-year-old son, and a white union organizer.
The story is told through the eyes of a Black janitor and single father. Racism is woven into the fabric of his life. He is extra diligent, for example, about polishing the brass in front of the apartment building where he works because he doesn't want to lose his job and be replaced by a white man. He knows he is vulnerable, and his boss dislikes him for pursuing an education. Further, when the janitor is approached by a union organizer, he immediately reacts negatively, feeling that unions are only for whites and that the union will replace him with a white man.
We see the effects of racism on the white organizer when he shows the narrator how his hands were burned and scarred by gasoline after he defended a Black man against unfair rape charges. We also see the effects of racism on the janitor's four-year-old son, who is already internalizing his racial limitations. For example, the boy aspires to the low-level goal of driving a delivery truck and wearing a hat with buttons because that is what he sees another Black person doing.
Through showing us how Black people, or white folks who work to help Black people, experience racism, Ellison builds a sympathetic picture of the fears and struggles that Black people face on a daily basis. Racism in this story is not theoretical, but a lived experience that impacts every aspect of life.