The central question that lies behind this famous poem concerns the origins of evil. The tiger in this poem is seen as a pure expression of malevolence and power in its strength and majesty. However, when read with its companion poem, entitled "The Lamb," the speaker is greatly troubled that both are part of God's created natural order and yet both are so incredibly different in terms of form and power. Thus the speaker finds himself profoundly disconcerted about the presentation of the tiger and has to ask himself, again and again, "What immortal hand or eye / Dare frame they fearful symmetry?"
The quot you have highlighted represents two more rhetorical questions that discuss the origins of the tiger and, by extension, of evil in the world. The speaker finds it difficult to understand how God could have "smiled" to see the tiger, because it is such a powerful and ferocious creature. He has to ask whether the tiger originates from the same God that made the lamb, as the two creatures are so incredibly different.