It's like you have a social security number or other ID number, which positively--there might be another person with the same name as you, God forbid, but you at least have your own number, which is guaranteed to be unique to you.

就好比社保号,或者其他身份号码,很有可能,有另外一个人,和你重名,希望这不要发生,但你至少有唯一的识别号,用于区分自己和他人

耶鲁公开课 - 金融市场课程节选

So every security has an identical CUSIP, which identifies it.

同样,每种证券都有CUSIP号用于区分

耶鲁公开课 - 金融市场课程节选