It's the difference between a pass and a fail.

　　這是及格和不及格的區(qū)別。

　　It took a practised eye to spot the difference.

　　只有內(nèi)行人才能看出其中的差異。

　　Can you spot the difference between these two pictures?

　　你能不能看出這兩幅畫有什么不同？