Before transmitting over the internet, data is divided into smaller pieces called network packets. The Internet uses TCP (Transmission Control Protocol) to compile and send packets of data safely. They contain a header, payload, and trailer.
Networks that use TCP/IP are Packet Switched Networks (PSN). The transport layer of TCP/IP breaks the data down into smaller pieces (network packets) to improve transmission efficiency. Error checking data may get packaged in the footer when the packets are created.