Cookies are just small .txt (text) files that by themselves cannot hurt your computer. Cookies are "set" by almost EVERY web-site that you visit, on every visit. You can delete all your cookies today and by tomorrow you will have dozens again just be visiting web-sites. Cookies do NOT slow down a computer, at least the first million or so that you might have on your computer! They are not a virus or spyware, but SOME people consider "tracking" cookies to be an invasion of privacy.
These tracking cookies are "3rd party cookies" from advertising servers. They can track your movements around the web in order to deliver to you customized, targeted advertising. It all depends on ones personal level of paranoia, whether one considers tracking cookies some kind of threat. Some anti-spyware programs do not even report tracking cookies as even a minor threat.
If these tracking cookies DO bother you AND you are using Internet Explorer for a browser, a simple change of a setting can let you permanently block all 3rd party (tracking) cookies. (Much easier then constantly removing them!) Go to tools > internet options > privacy > advanced > check-mark "override automatic cookie handling" > third party cookies > tick "block" > ok > ok.
A cookie is a plain txt file that sits on your computer in a temporary folder that stores data about a browsing session. If you log into a website it generally sets a cookie to temporarily store your information so you don’t have to log in every time you change a page.
A tracking cookie is a cookie that tracks your browsing behaviors. Marketers use this data to understand how users use their partner websites and optimize their networks for the average user that visits their networks.
Some people hate cookies, claim they’re spyware, and always delete them. Personally, we’re not exactly worried about them: unless you’ve shared your personal information, the tracking cookies are only going to report browsing habits which helps generate a bunch of marketing statistic.
Really, we think the only time you need to worry about cookies is when you’re on a public computer – like at school or an Internet cafe. In this instance, you should clear the cookies after you’re done so any stored information – such as login information – will not be stored on that computer.