"Les" is a French definite article used to indicate plural nouns. It is equivalent to "the" in English and is used before nouns that are known or specific to the speaker and listener. For example, in the phrase "les livres," it refers to "the books," implying that both the speaker and listener are aware of which books are being discussed. In French grammar, "les" is part of a system that includes other articles like "le" for masculine singular nouns and "la" for feminine singular nouns. Understanding how to use "les" correctly is essential for proper communication in the French language, as it helps clarify which items are being referred to in conversation.