Packet switching breaks data into packets that may take different paths to the destination — each router makes independent forwarding decisions. The basis of the internet (IP/TCP).
Packet switching vs. circuit switching (dedicated path, like traditional PSTN phone). Packet switching: efficient, resilient (route around failures), variable delay. Circuit switching: guaranteed bandwidth and latency, wastes resources when idle. Internet = packet switching. MPLS provides some circuit-switching qualities in packet networks.