What's the difference between 是不是 and 对不对？
We sometimes translate both 是 and 对 as &quot;yes&quot;.  However, they're very distinct in meaning: 是 is a verb meaning &quot;is&quot;, whereas 对 is an adjective meaning &quot;correct&quot;.  (Putting aside how both 是 and 对 have multiple other meanings.)

她是你女朋友。
She is your girlfriend.
对，她是我女朋友。
Correct Yes, she is my girlfriend.

We translate 对 to &quot;yes&quot; in English because &quot;correct&quot; sounds overly formal.
We might instead reply using the verb 是:

是，她是我女朋友。
Yes, she is my girlfriend.

We don't really have an equivalent to this in English.  By repeating the verb 是, we affirm the previous statement is correct.  Otherwise we might say one of:

不对，她不是我女朋友。
Incorrect No, she is not my girlfriend.


不是，她不是我女朋友。
No, she is not my girlfriend.

We can use 是不是 and 对不对 as affirmative-negative questions:

你有儿子，是不是？
你有儿子，对不对？ [equivalent]
You have a son, right?
你是不是我妈？  [here we cannot use 对不对 instead]
Are you or are you not Are you my mother?
他的行为对不对？  [here we cannot use 是不是 instead]
Is his behavior correct or not correct correct?

And many verbs and adjectives can be used this way.

你吃不吃？
You eat or not eat Do you want to eat some?
你有没有手机？
Do you have or not have have a mobile phone?


天气好不好？
Is the weather good or not good good?
你的皮肤白不白？
Is your skin white or not white white?

Furthermore, these constructions are sometimes used outside of questions, e.g.:

我不知道他是不是结婚了。
I don't know if he is or not is is married.