Answer
As a protocol droid, C-3PO's primary function is to assist in communication and etiquette. Equipped with an extensive database of languages and customs, he serves as a valuable mediator between humans and other species, facilitating smooth interactions and ensuring diplomatic protocol is upheld during negotiations and encounters. Additionally, C-3PO's programming includes knowledge of etiquette, customs, and languages from across the galaxy, making him an invaluable asset in diverse social situations.