lord of the rings // legolas
I think they're the same race/species, but different breeds? If that makes sense? Apparently "goblin" was the term Tolkien used in The Hobbit (which was before he wrote The Lord of the Rings), but he switched to "Orc" for LOTR and only the Hobbit characters tend to refer to them as "goblins."

I got all this from the Orc Wikipedia page, btw.