A Cookie is small size file which a website sends to the browser and saves on your computer when you visit a websites. Cookies are allowed to enhance the websites operations, but also you have to provide us with the inforamtion on the site.
Web browsing cookie:
Cookies may reflect the de-identified demographic or some other data which is linked to data you have voluntarily have submitted. Basically cookies cannot harm your computer. In general it is not what cookies can do to your computer,but what information they can store and what can pass on to servers.
This cookies are important to allow the user to search the site and use it functions such as loggin the websites reserved area. Without these kind of reqsuet the the loggin to the reserved area cannot be provided the service requested.
These cookies are used by google Analytics good example of it are Google Doubleclicks, Google adwords, Facebook. These kind of cookies are not active yet.