Rules of Packet Transmission
Data is sent around the Internet in chunks called Packets. This method is called Packet Switching.
How it works
Imagine two computers X and Y. They are both connected to the Internet. Computer X wishes to send a message to Computer Y. Computer X splits the message into chunks and then generates as many packets as there are chunks. Each chunk is placed into the Payload part of the next available packet.
The unique address of the sending computer is placed in the Source address part of each packet and the unique address of the receiving computer is placed in the destination part of each packet. Each packet is then dispatched to the Internet through a router gateway.
The packets are sent independently through a series of interconnected routers until they reach their destination. Each router examines the destination address of a packet to determine what to do with it. Computer Y receives the packets and re-assembles them to get the original message.