Juxtaposition

Juxtaposition is a literary device that involves placing two or more things side by side to compare or contrast them, or to create an interesting effect. Juxtaposition can be used to:
(a) Highlight differences and similarities
(b) Enhance the mood or theme of a story
(c) Emphasize the attributes of each element

Examples:

• Contrasting ideas, such as good and evil, or light and darkness
• Youth and old age to showcase themes of innocence versus wisdom
• East Egg and West Egg in The Great Gatsby: "old money" versus "self-made man"