Чем гоблины отличаются от орков ?

  Hе доказано. Это лишь одна из версий. Есть мнение, что "оркор" - собирательное название ВСЕЙ нечисти.

1. Внешним видом. причем очень сильно. Орки зеленые и чаще всего с человека размером, гоблины они поменьше и волосатые.
2. происхождением.
3. Отношением к людям, эльфам, гномам, etc. подразумевается наличие первого гнома, который имел хорошие отношения с горными орками, потом они переругались все равно, но гномов орки любят больше чем людей и конфликтуют с ними реже.
4. в принципе разные линии развитя нелюди.

  What was the relationship between Orcs and Goblins?

They are different names for the same race of creatures. Of the two, "Orc" is the correct one. This has been a matter of widespread debate and misunderstanding, mostly resulting from the usage in _The Hobbit_ (Tolkien had changed his mind about it by LotR but the confusion in the earlier book was made worse by inconsistant backwards modifications). There are a couple of statements in The Hobbit which, if taken literally, suggest that Orcs are a subset of goblins. If we are to believe the indications from all other areas of Tolkien's writing, this is not correct. These are: some fairly clear statements in letters, the evolution of his standard terminology (see next paragraph), and the actual usage in LotR, all of which suggest that "Orc" was the true name of the race. (The pedigrees in Tolkien: The Illustrated Encyclopedia are thoroughly innaccurate and undependable.)

What happened was this. The creatures so referred to were invented along with the rest of Tolkien's subcreation during the writing of the Book of Lost Tales (the "pre-Silmarillion"). His usage in the early writing is somewhat varied but the movement is away from "goblin" and towards "orc". It was part of a general trend away from the terminology of traditional folklore (he felt that the familiar words would call up the wrong associations in the readers' minds, since his creations were quite different in specific ways). For the same general reasons he began calling the Deep Elves "Noldor" rather than "Gnomes", and avoided "Faerie" altogether. (On the other hand, he was stuck with "Wizards", an "imperfect" translation of Istari ('the Wise'), "Elves", and "Dwarves"; he did say once that he would have preferred "dwarrow", which, so he said, was more historically and linguistically correct, if he'd thought of it in time ...)

In _The Hobbit_, which originally was unconnected with the Silmarillion, he used the familiar term "goblin" for the benefit of modern readers. By the time of LotR, however, he'd decided that "goblin" wouldn't do -- Orcs were not storybook goblins (see above). (No doubt he also felt that "goblin", being Romance-derived, had no place in a work based so much on Anglo-Saxon and Northern traditions in general.) Thus, in LotR, the proper name of the race is "Orcs" (capital "O"), and that name is found in the index along with Ents, Men, etc., while "goblin" is not in the index at all. There are a handful of examples of "goblin" being used (always with a small "g") but it seems in these cases to be a kind of slang for Orcs.

Tolkien's explanation inside the story was that the "true" name of the creatures was Orc (an anglicized version of Sindarin *Orch* , pl. *Yrch*). As the "translator" of the ancient manuscripts, he "substituted" "Goblin" for "Orch" when he translated Bilbo's diary, but for The Red Book he reverted to a form of the ancient word.

[The actual source of the word "orc" is Beowulf: "orc-nass", translated as "death-corpses". It has nothing to do with cetaceans.]