What is Packet?
A packet is a self-contained bundle of data sent over a packet switching network. Packets are typically less than 1500 bytes in size. Longer files are broken into multiple packets for transmission and reassembled at the other end.
A packet includes a header with to and from addresses, relation to other packets (sequencing), and error checking information. When the data reaches its destination, the protocol makes sure that all packets arrived without error. On the Internet, datagram is a synonym for packet.