Session management (PHPSESSID, SSID_)

They are identifiers of the browsing session. They can be used to recognize the user and maintain the logged in status when visiting new pages.

User registration (Users, Ecommerce)

They allow the site to recognize the user if the site has user registration functions (e.g. restricted areas, e-commerce).

Google Analytics (__utma, __utmt, __utmb, __utmc, __utmz, __utmv)

As a user navigates between web pages, you can use the analytics.js tagging library to record information about the page the user has seen (for example, the page's URL) in Google Analytics. The analytics.js tagging library uses HTTP Cookies to remember the user's previous interactions with the web pages.