X.25 is a standard protocol for packet-switched networks, developed in the 1970s. It allows for the transmission of data over a network by breaking it into smaller packets, which can be sent independently and reassembled at the destination. This method improves efficiency and reliability in data communication. The X.25 protocol operates at the network layer of the OSI model, providing error correction and flow control. It was widely used in early computer networks and is still relevant in some legacy systems today, although newer technologies like TCP/IP have largely replaced it in modern applications.