What is a “cookie”?
They can do this because when you return to a webpage that has sent a cookie to your computer previously, that webpage can then access that cookie and the information it holds. For example, a cookie can save preferences you have set on a webpage such as the preferred text size; or a cookie can save information for you such as a username or even a password, meaning that you do not have to type them in every time you visit the page. Additionally a cookie can provide information to the users of a site to help them make the the site work more efficiently.
For a full description of the various types of cookies and what exactly the new rules governing their use are, visit www.allaboutcookies.org. You can also check out a short video on cookies by visiting www.google.co.uk/goodtoknow/data-on-the-web/cookies.
You should be aware that websites depend upon cookies for full functionality and that should you disable all cookies, you may not be able to use the website properly and may be unable to access some parts of the website.