Functional cookies
Functional cookies remember choices and enable features that improve a website without being essential to it, such as a saved language, a region, a video player setting or a chat widget, and they usually require consent.Functional is a category used by consent tools, not a term defined by law. It sits between strictly necessary cookies and analytics: the cookie serves the visitor rather than the site's marketing, but the site would still work without it.
The legal question is whether the feature was explicitly requested. Article 5(3) of the ePrivacy Directive exempts only storage that is strictly necessary for a service the user asked for. A language cookie set when the visitor picks a language from a menu can meet that test, and the Article 29 Working Party's Opinion 04/2012 treats such user-interface customization cookies as exempt when they are limited to that purpose. A cookie that guesses preferences, personalizes content on its own initiative, or comes from a third-party widget the visitor never opened does not, and needs consent.
Third-party functional tools are the usual issue. Chat widgets, embedded maps, video players and font services often set cookies or collect the IP address as soon as they load, so a banner holds them until the functional category is accepted, or shows a placeholder until the visitor clicks. See YouTube embeds and consent for the placeholder approach.