A packet is a piece of message that us transmitted over the network and follow the packet switching network to send receive messages on every computer or we can say a network as packet switching network. Example every web page that you receive comes not exactly as you think it comes in the series of packets, and the process is same for every message you send and receive. Message travels in packet switched network that ship data around in small packets. Like an e-mail message network divide into several bytes with the destination address and send the packet over internet. The packet carry the data with some standard sets of protocols that internet use like TCP/IP. A packet contain 1,000 or 1,500 bytes. Packets are also known as datagrams in IP networks.
Packet switching refers to a protocol in which packets are transmitted from one place to another, messages are divided into packets before they sent. Each packet transmitted individually in the network and can follow different paths(routes) to its destination, Then at the receiver end once the all packets of the same message arrive then they compiled to the original one. Modern Wan protocols are TCP/IP, x.25 both of them are based on packet switching technologies. Whereas telephone services are based on circuit-switching network in which a dedicate line is allocated between two parties to establish effective communication. But packet switching network has its advantage to use over circuit switching network because they are robust for data that can withstand some delays in transmission like email and web pages.