The internet, as it is called in the vernacular, is a packet-switched network. This means that each transmission of, for example, a file, is broken onto packets of information, and each one contains the source and destination information, a sequence number that indicates what order the packets are supposed to be re-assembled in, a code that can be used to correct errors or identify bad packets, along with the actual payload data. Special computers called switches and routers read the source and destination data and send the transmitted packet to the correct digital address, ideally by the shortest timewise route, but not always. the many packets that contain a single file may individually be sent along several paths to get to the destination, depending on congestion and load and latencies. The received packets are stored in the destination equipment until all are present and any defective packets have been re-transmitted and received and checked again, then the original file is re-assembled in the correct order for use.