I don't understand the meaning of the sentence.
After all a map only has a tiny bit of "edge" but plenty of "middle" in which your destination could be situated. Or has it?
1. What does "Or has it" mean?
2. What does "Or" mean?
3. Why "has" is used here?
4. What does "it " refer to?
5. When and how to use such a sentence pattern?

Question

I don't understand the meaning of the sentence.
After all a map only has a tiny bit of "edge" but plenty of "middle" in which your destination could be situated. Or has it?
1. What does "Or has it" mean? 
2. What does "Or" mean?
3. Why "has" is used here?  
4. What does "it " refer to?
5. When and how to use such a sentence pattern?

Answer

"Or has it?" means "Or does it?" in American English. It is asking if the following sentence is true. So "Or does it have only a tiny bit of edged and plenty of 'middle' in which your destination could be situated?"