An ISBN gets placed on the copyright page and, if there is no bar code, on the back cover.

What is the difference between a bar code and an ISBN?

An ISBN is a number. A bar code is the graphic with vertical lines that encodes numerical information for scanning purposes. An ISBN and a bar code are two different things.

Are different ISBNs used if a book appears in different languages?

Yes. Each language version is a different product.

If the price of the book changes, does the ISBN?

No. The ISBN only changes if the product changes.

If typos are being corrected, is a new ISBN necessary?

No.

Can an ISBN be reused?

No, once a title is published with an ISBN in it, the ISBN can never be used again. Even if a title goes out of print, the ISBN cannot be reused since the title continues to be catalogued by libraries and traded by used booksellers.