A Data Transfer Protocol is a set of rules that governs how data is transmitted over a network. It ensures that information is sent and received accurately between devices, such as computers and servers. Common protocols include HTTP for web traffic and FTP for file transfers, each designed for specific types of data exchange. These protocols define how data packets are formatted, addressed, and checked for errors during transmission. By following these guidelines, devices can communicate effectively, allowing users to access websites, download files, and share information seamlessly across the internet.