If we want to find out whether there is any difference between two similar things, I heard the following ways of asking about it (the first being more common):
"What makes them different"?
"What is it that makes them different?"
At first, both questions seemed same in meaning and but when compared, I think there is a small difference between the two questions.
Although, both questions ask the same thing(s, the second one assumes there is probably 1 thing that is different. And the first question does not care about how many differences there may be in number.
This is what I think, however because English is not my native language, I can't be quite sure.
Am I right in my thinking?