A file of minute proportions that is saved on a mobile device or a computer that stores important information relating to the interaction of the user with the site. By accessing the cookies on a computer you can track what sites have been visited, and the exact pages within that site.
When sharing a computer, or using a computer in a public building such as a library it is vital that you clear the cache of cookies before logging out for security reasons. When you fail to clear your cookies, people can access your personal details, and the professional hacker can steal your identity in just seconds.
Cookies were created and designed to save user information so that a web server can deliver a web page tailored to the specific user. It allows form data to be maintained, and can improve the user experience by maintaining data from one visit to the next. Cookies are a very convenient way to maintain information from one session to the next, or even to carry information from one website to another.
Cookies also lower the burden on web servers since the data stored by the cookie does not have to be stored on the server. In fact, storing such information server side would be problematic since it would require a user to log in again every time they visit a website, or even navigate to another page.
Cookies are designed to be destroyed when the web browser is closed, but can also be set to persist for any length of time, even indefinitely.
One evolution of the cookie is its use in commercial websites, which now include embedded information from third-party sites. This usage makes it possible for a website to access cookies from another site and deliver advertisements based on the information stored in the cookie. This information could include the name of the site, products viewed when there, pages visited, or other relevant data. This allows advertisers to serve ads that are tailored to a users interests and buying habits. In theory this is meant to be more useful to users, however many of them see this usage as an invasion of their privacy since advertisers can use cookie information to build profiles of users without their permission.