The core technologies of the web are stateless, a fancy word to say that interactions between users and web applications are normally not recorded and hence a web application has no way to know that a user has visited the site before and is returning.
Cookies are a mechanism that gives web applications memory; when cookies are enabled, web applications can store a small amount of data on the user’s computer. When the user visits the same site again, this little bit of data, called a cookie, is sent back to the web application.
The user is in control and owns all the cookies stored on the computer; search “clear cookies” to know how to destroy some or all the cookies on yours.
Types of cookies
There are two main kinds of cookies: technical cookies and profiling cookies.
Technical cookies are used merely for the purpose discussed in the previous paragraph; endow the web with memory. The prime example of a technical cookie is the session cookie, used virtually by any web application to keep you logged in even after you close the browser, so that you do not have to login every time.
Profiling cookies are used to track browsing behavior so that the web application can offer a more personalized browsing experience to the user. The best known example of profiling cookies are those used by ad-syndication networks; thanks to profiling cookies, you are less likely to receive ads for things that you do not care about.
This website participates to Google’s AdSense program. Profiling cookies are used to increase the chance that the ads that we show you are relevant for you. Participation to ad-syndication programs and adoption of profiling cookies are commonly seen in websites that offer free content.
Ultimately, you are in control of your cookies. In addition to being able to delete them at any time, you can also customize what advertisers can do with them. See Google Ad Settings and WebChoices by DDA for more info.