Why does putting a piece of bread in a container of cookies allow the cookies to stay soft while only the piece of bread hardens?

Question

My baker friend taught me this trick. I’m mystified and don’t understand how it works.

In: Other

Answer 1

Bread’s job application: Moisture lifeguard. Cookies’ job application: Crumbly crunch providers. Outcome: Moisture-rich, soft cookies and a hardworking, hardened piece of bread.