Packet switching is the process of routing packets over a network comprised of switching nodes and and shared data links. The shared data links are data paths between the switching nodes. The switching nodes are typically routers.
Messages are broken into small blocks of data which are called packets. Packets contain destination information along with data and error checking information. Messages are sent between computers by sending the packets through the network. The receiving computer will re-assemble the packets to create the original message.
When packets are sent through the network, the nodes or routers will normally route the packets from node to node using the most effective route. The routing method may be static where the node will always route packets the same or the routing method may be dynamic where a routing protocol may update the router concerning changes to the network. Therefore packets associated with the same message may be routed through a different network path than other packets associated with the same message.