If issuing the command:
Then the local device generates an ICMP Echo (Type 8, code 0) which is sent outbound. The device then waits to receive an ICMP Echo Reply (Type 0, code 0).
If the packets TTL expires before reaching its destination, then an ICMP Time Exceeded (Type 11, code 0) packet is sent to the originator of the ICMP Echo.
When using Traceroute and the ICMP packet reaches the final destination, normally a ICMP Port Unreachable (Type 3, code 3) will be sent back towards the source.
If a device in the forwarding path does not know how to route towards the destination it will send an ICMP Net Unreachable (Type 3, code 0). This is true no matter what kind of packet was sent from the beginning, ICMP or not.
Note that many administrators filter ICMP (often on lacking knowledge) so that ICMP packets may not be received back.