network packet
A data packet (English: ), also known as a packet, is a formatted unit of data transmitted in a packet-switched network .
A data packet (packet) is divided into two parts, including control information, that is, header data (header), and the data itself, that is, payload (payload).
We can compare a data packet to a letter, the header data is equivalent to the envelope, and the data part of the data packet is equivalent to the content of the letter. Unlike letters, sometimes a large data packet can be divided into multiple small data packets.
OSI model
In the OSI model , a data packet is the name for the data unit of the third layer.