Self-referentiality is a concept where something refers to itself. This can be seen in language, art, and mathematics. For example, a sentence like "This sentence is about itself" is self-referential because it describes its own content. In literature, self-referential works often break the fourth wall, acknowledging their own fictional nature. A famous example is the book Don Quixote by Miguel de Cervantes, where the characters are aware they are in a story. This technique invites readers to think critically about the nature of reality and fiction.