Cookies are tiny files stored by your browser (A browser is the piece of software you use to view the World Wide Web. Microsoft Internet Explorer, Google Chrome and Apple Safari are all examples of browsers). Most cookies are simple text files (as ours are), so it's impossible for them to carry viruses, and your browser's own security does a great deal to police how they operate. They're stored in a specific area on your machine and have to adhere to strict rules. You can look at the cookies on your machine by using your browser's settings. All browsers have their own way of doing this, so check the Help for the one you're using.
The World Wide Web is designed to protect your security and privacy. For example, when you access a website, the server providing you with the page your requested has no method of knowing who you are. When you ask for another page on the same site, the server doesn't know that you're the person who just read the home page.
This is inconvenient though when you need to carry information from one page to another. If you buy something online you'll store your intended purchases in a shopping basket, then move on to a secure connection to enter your payment details. You wouldn't want to have to re-enter what you're ordering every time you move on. To save you the trouble, your progress through the site is saved in a cookie so that each new page can access the choices you've made.
The cookies that we use for this purpose contain only information relating to this site, and are not personally identifiable. They expire and are deleted from your machine within 30 minutes of your leaving the site.