Digital Router Question:

To make a baseband network practical for many computers to share, the data transmitted by each system is broken up into separate units called packets. When your computer transmits data it might be broken up into many packets, and the computer transmits each packet separately. When all of the packets constituting a particular transmission reach their destination, the receiving computer reassembles them back into original data. This is the basis for a packet-switching network.
Circuit-switching means that the two systems wanting to communicate establish a circuit before they transmit any information. That circuit remains open throughout the life of the exchange, and is only broken when the two systems are finished communicating. Circuit switching is more common in environments like the public switched telephone network (PSTN), in which the connection between your telephone and that of the person you're calling remains open for the entire duration of the call.