Complex sentence: Unlike the goblins in Tolkien's works, the goblins of D&D are a separate race from orcs; they are a part of the related species collectively referred to as goblinoids, which includes hobgoblins, bugbears, and others.
Split into simpler sentences: Unlike the goblins in Tolkien's works, the goblins of D&D are not smaller cousins of orcs. Instead, they are a part of the related species collectively referred to as goblinoids, which includes hobgoblins, bugbears, and others.