It’s Nothing: Used to tell someone not to worry about, or place special value on, what you are doing or have done; Used as a polite reply when someone has thanked you for doing something for them; To tell someone that the task you did was not a big deal. It is commonly used when you are being thanked for something that wasn’t difficult. As in No need to thank me. It’s nothing.
中文释义：It’s nothing是没事，小事情，不足挂齿的意思。 当别人感谢你为他们做的事情时，用作礼貌的回答，告诉别人你做的事情不是什么大事，小事情不足挂齿。还可以用在不向别人抱怨带有负面情绪的事情。比如：你心情不好，别人问你“ what’s wrong?”时，你不想谈论，就可以回答“ It’s nothing.”