A data packet is a formatted unit of data carried by a packet-switched network. It contains both the payload, which is the actual data being transmitted, and control information, such as the source and destination addresses. This structure allows networks to efficiently route and manage data transmission. When data is sent over the internet, it is broken down into smaller packets to ensure reliable delivery. Each packet can take different paths to reach its destination, where they are reassembled into the original message. This process is essential for the functioning of the Internet Protocol (IP) and other networking protocols.