Final answer:
Traceroute is a command-line tool that uses ICMP to trace the route that a packet takes to a host.
Step-by-step explanation:
Traceroute is a command-line tool that uses Internet Control Message Protocol (ICMP) to trace the route that a packet takes to a host. When a traceroute command is executed, the tool sends ICMP echo request packets with varying Time-To-Live (TTL) values. As the packets traverse through different routers and networks, each router decrements the TTL value and sends an ICMP time exceeded response back to the sender, revealing information about the path taken by the packet.