Cookies are a technical mechanism, consisting in small text files, that store information provided by the user, at its first access. When the browser accesses again the same server, the cookie (with the stored information) is sent back by the browser to the server, to make the contained information available to it.

A cookie can be removed explicitly (with the tools provided by the browser) or automatically when the connection is closed, as an alternative a cookie can remain stored in a browser for the created expire time that can range from seconds to years.

At the beginning, the cookies (Technical cookies) were used to store session information regarding the specific site (storing user details, passwords, form data, language and date format, preferred time-zone…, etc.) and for improving the fruition of the services there hosted.

Then websites started to use them (Profiling cookies) to track users, collecting their preferencies and profiling their habits. The profiles so built are mainly (but not only) used to send customized advertising messages.

Depending on the destination of the information contained in the cookie they can be furthermore classified as:

• First party cookies The information contained in the cookies are sent from a server (beloging to an internet domain) to the browser and then the browser will send this information back to the same server (or to a different server, but always, belonging to the same domain).
• Third party cookies. The information contained in the cookies are sent from the one server (in a domain) to the browser, and the contained information are then made available to a different server (in a different domain from which it came from).