Cookies
 

I received a question, via private messaging, regarding cookies. I believe that the purpose of the forum is best served by such questions being public, so that the responses may serve members other than the original poster. Consequently, I am posting that question here.
A cookie is a text entity that is sent to your browser by the sever. The information it contains is returned to the server when the client submits a request to that server. As a text entity, it can perform no active tasks on the client. It may be used, however, to store (and pass along) private information that the server may be able to obtain in the process of conducting transactions with you. With any decent browser, you have the option of rejecting cookies, viewing the cookies stored, and of deleting those cookies.

One use of cookies to identify you so that any preferences you have indicated to the server, perhaps in regard to how you view the site, can be fetched and put in place each time you access that site. Cookies are also one way to maintain state (session continuity) throughout a series of request/response transactions, since HTTP is a stateless protocol.

I am not a big fan of Wikipedia, but you might want to read this, or similar information that you can easily find via Google or another search engine.