Please note that this is a human translation from catalan; my english is self learned and not my main language, so please excuse any grammar mistakes.
By accessing to the mapping.barcelona site, or starting session in an hypotetical private area inside, the website sends you an encrypted session cookie. A session cookie is a temporary cookie that remains stored in your computer just until you leave the website. This cookie is used to validate your access to certain areas on the website.
Enabling and disabling cookies
You can accept or deny cookies storage by modifying your browser settings. But you should be aware that this can affect the way you use this website, e.g. whether you’re able to login or not among other issues. You can always manually delete cookies from your computer. If you need more information on how to enable or disable cookies, check the help docs on your browser or operating system.
I took this website and other sources as a reference to write this content.