A cookie is a small file which is stored securely on your computer's hard drive.
The cookie file helps website owners to analyse web traffic or respond to the user with individual or personalised content. A modern website can tailor its operations to the user's needs, likes and dislikes by gathering and remembering preference information, which it stores in a cookie.
Overall, cookies help us provide you with a better website by enabling us to monitor which pages you find useful and which you do not. A cookie in no way gives us access to your computer or any information about you.
Most web browsers automatically accept cookies but you can usually modify your browser setting to decline cookies if you prefer. This may prevent you from taking full advantage of this and other websites though.