Cookies may be set by the website you are visiting (‘first party cookies’) or they may be set by other websites who run content on the page you are viewing (‘third party cookies’).
What is in a cookie?
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.
What if I don't want cookies to be set?
"Some people find the idea of a website storing information on their computer or mobile device a bit intrusive, particularly when this information is stored and used by a third party without them knowing. Although this is generally quite harmless you may not, for example, want to see advertising that has been targeted to your interests. If you prefer, it is possible to block some or all cookies, or even to delete cookies that have already been set; but you need to be aware that you might lose some functions of that website."
[Source: BBC.CO.UK 'about cookies']
How can I control cookies?
"If you wish to restrict or block web browser cookies which are set on your device then you can do this through your browser settings; the Help function within your browser should tell you how. Alternatively, you may wish to visit www.aboutcookies.org, which contains comprehensive information on how to do this on a wide variety of desktop browsers."
[Source: BBC.CO.UK 'managing cookies']