Why does Yii2 need cookieValidationKey?

Question

Yii

Good afternoon, please tell me what this key is for, and why cookie validation is needed in general (if I put it correctly)

Answer 1

Good evening.
Cookies ans Sessions

Answer 2

I can just guess. It takes the key from the cookie and does a validation against the database.
Perhaps this is done so that a person enters the site and automatically generates a cookie, then picks up the goods in the basket, where the goods are associated with the cookie.
Closed the tab.
I opened the tab again, the site and looked for cookies in the database and filled the basket with the latest products.