What does the output of traceroute mean?

Solution 1:

From the man page of traceroute:

This program attempts to trace the route an IP packet would follow to some internet host by launching UDP probe packets with a small ttl (time to live) then listening for an ICMP "time exceeded" reply from a gateway. We start our probes with a ttl of one and increase by one until we get an ICMP "port unreachable" (which means we got to "host") or hit a max (which defaults to 30 hops & can be changed with the -m flag). Three probes (change with -q flag) are sent at each ttl setting and a line is printed showing the ttl, address of the gateway and round trip time of each probe.

So, 75 ms 71 ms 73 ms stands for the round trip time it took for each different probe.

Solution 2:

Each entry is the RTT (round-trip time) for a particular probe to a particular host. I.E., the RTT times for the second hop host (reserve.cableplus.com.cn) were 75 ms, 71 ms, and 73 ms for the first, second, and third probes respectively.

On Linux, you can change the number of queries/probes to each host with -q.