"which" and "in which"

I'm an English learner.
I see lots of sentences with phrase "in which" in the textbook.
What is the differences between the use of "which" and "in which"?

[Dany]

Hello elieli123,

"in which" refers to the context.
Example: There is an grammar book in which you can find more information.
in which = in the book

"which" refers to the object
Example: There is a new drug on the market which will destroy cancer.
which = a new drug

I hope that this is helpful for you

[elieli123]

Thank you Dany~!!

Your explanation is so clear to understand:)

I really appreciate your help~!

[Dany]

You're welcome