The structure 不是…就是…
With this structure, we talk about situations where there are only two possibilities.
We use the structure 不是…就是… 
to describe that there are only two possible options: either the first or the second.
We can use any part of the speech inside the structure: verbs, adjectives, pronouns, nouns.
to describe that there are only two possible options: either the first or the second.
We can use any part of the speech inside the structure: verbs, adjectives, pronouns, nouns.Scheme
不是
A
就是
B
Examples
他不是玩，就是学习
He either plays or studies
tā bú shì wánr, jiù shì xuéxí
我不是在书店，就是在图书馆
If I'm not in the bookstore, I'm in the library
wǒ bú shì zài shūdiàn, jiù shì zài túshūguǎn
不是你就是他得把报告交上来
Either you or he has to make the report
bú shì nǐ jiù shì tā děi bǎ bàogào jiāo shànglái
Pay attention
Be careful and do not confuse this with the structure 不是…而是… . Read more about it here ↓
. Read more about it here ↓