What is a tracking Cookie?
A tracking cookie is a file that stores information on where you have been and where you have visited. Most websites gives you a tracking cookie so they know what you did on there site. For example, comcast.net gives you a tracking cookie so comcast knows what you did on their site. But some websites give you what is called an advertising cookie. which is a tracking cookie that is exactly what user goran said. examples of advertising cookie web sites. (sites that give you advertising cookies) here are five examples: doubleclick.com, advertising.com, atdmt.com, tacoda.net, edge.ru4.com, and very very much more.
A tracking cookie is a small file that is saved on your computer when you visit a website. Sometimes the cookie is placed on your computer by an advertisement. When you go to another website that uses the same company for advertisements, they can read the cookie and see where you've been. Most times the cookies are harmless, but sometimes they're not. For some websites, the cookies store the username and password you used for that website. The when you go to another website, they can see where you've been and read the username and password that is stored in the cookie.
sorry I did not tell you this before but MOST tracking cookies are not bad. just all advertising cookies are BAD!!!