just the difference between them is confusing me...
Also, often intermediate routers (internet backbone routers and such) are configured to not respond to ICMP (ping) packets, which is why trace route times out on several of the hops for traces across the internet. So summing the hop times is not possible when any intermediate router refuses to respond to ICMP.
When you do a traceroute, you are actually sending several packets, with incremental TTL (time to live).
First packet will hit the first "hop", and come back, you will get the ping time to this place. Same for second packet, which will stop after the second "hop", and so on. Each "ping" you get in a traceroute is the time to each intermediate router, from you, and not the time between two routers.
In traceroute, only the final packet, the one which reached the destination and came back, is the actual ping from you to this place.
You can find further details on how traceroute works, on the wikipedia article.