The Information Commissioner describes cookies (and similar technology) as "a small file of letters and numbers that is downloaded on to your computer when you visit a website. Cookies are used by many websites and can do a number of things, eg remembering your preferences, recording what you have put in your shopping basket, and counting the number of people looking at a website".
In addition, where websites allow users to log in to services, authentication cookies are the most common method used by web servers to know whether a user is logged in or not.
Tracking cookies, and especially third-party tracking cookies, are commonly used as ways to compile long-term records of individuals' browsing histories.
The law distinguishes between "strictly necessary" cookies, such as those which enable websites to operate properly, or which allow purchases to be safely completed, and those which are not strictly necessary, such as tracking cookies, or cookies used for the purposes of web analytics.
We are allowed to place strictly necessary cookies on your device without your consent (as long as we inform you, such as by way of this notice), but for all other cookies we require your express consent. This is why we have a clear "cookie banner" when you land on our website, which allows you either to consent to receive these "non-necessary" cookies, or decline them.