Cookie
A piece of code containing user information.
A cookie often contains the user's login name, password, preferences, and shopping cart info which is first sent by a server to your browser when you logon, then returned to the server upon request, containing the information requested.
Cookies generally expire after a given amount of time and are sometimes saved on your hard drive when your browser closes, but they can’t read your hard drive or send information from it.
Most spyware programs consider cookies as low risk. On the whole, they are time savers for both you and the businesses you buy from online.
Keep in mind, though, that some users block cookies and that if cookies are required to access and navigate your site, users might be frustrated and leave, and also search engines will not be able to crawl your site.