A cookie is a small amount of data, which often includes an anonymous unique identifier, that is sent to your browser from a website's computers during your first visit and is stored on your computer's hard drive. When visiting the website again from the same device the cookie and all therein stored information will be sent back either to the website which created the Cookie (First Party Cookie) or to a different website it belongs to (Third Party Cookie).
Thus the website recognizes a repeated visit and may vary the content. Some Cookies are really useful as they can optimize the user experience by remembering your prefenreces and appropriately adjusting the content. If you would like to block or delete Cookies, you can do this by adjusting your browsersettings. To find our how to do this you may use the help-function of your browers or visit the website: http://www.aboutcookies.org