Langue d'Oïl refers to a group of Romance dialects spoken in northern France, which evolved from Latin. It is one of the two main branches of the Old French language, the other being Langue d'Oc. The term "Oïl" comes from the word for "yes" in these dialects, distinguishing them from the southern dialects. Historically, Langue d'Oïl was the language of the Capetian dynasty and became the basis for modern French. It played a significant role in literature and administration during the medieval period, influencing the development of the French language as we know it today.