A cookie is an item of data that a web site stores on a user's browser. They can be used for a variety of reasons, sometimes just to record that a browser is using a particular site, sometimes to store user preferences, and sometimes to track user activity across groups of co-operating sites.
We don't use cookies to identify or track people visiting this web site. The software that runs echomap requires the use of a 'session cookie' in order to operate, and it can't be disabled without changing the software.
You can learn more about cookies here.