From Urban dictionary : Another way of saying "whatever". It is often confused with "same thing", but you're really saying "OK, I admit that they're not the same thing, but they're not different enough for me to really care about it."
It means there is no significant difference between two choices. It was an expression which really upset the most stupid person in all history, my father. "Christ I hate that goddamn expression! How can a thing be the same and different?"
One that puzzles me is the Americanism "I could care less" compared to the British "I couldn't care less." The first make it clear that if you could care less then you must still care a little bit.