A cookie is a simple text file that is stored on your computer or mobile device by a website’s server and only that server will be able to retrieve or read the contents of that cookie. Each cookie is unique to your web browser. It will contain some anonymous information such as a unique identifier and the site name and some digits and numbers. It allows a website to remember things like your preferences or what’s in your shopping basket.
For more information see: www.allaboutcookies.org
Most browsers will enable you to manage your cookies preferences e.g. have the browser notify you when you receive a new cookie or use it to disable cookies altogether. If you do decide to disable or delete them altogether some sites won't work as well as they rely on cookies to provide you with the service you have requested (see Strictly Necessary cookies, above).