Question

what is importance of setting and unsetting the cookies data

Answer 1

Cookies help your browser to store some data about the website. Like when you go to any Social media site for the first time and login, then the login data is stored as cookies.
When you open the site for the second time the cookies stored let you to login with putting details for the second time.
This is a good feature which prevents additional usage of data and so most of the users prefer to keep the settings on.
Hope it helps you