[anshorei]

> what they do and why they are necessary should be explained to the user.

i.e. you need to add a popup or a banner

[herbst]

You don't need a popup for that. I just explain my cookie use in my privacy policy and never used a banner/popup

[kelnos]

No, a popup or banner would be for requiring consent. A non-consent explanation can be in the privacy policy, or on a dedicated page that is linked in the page's footer or something.

Also, "should" be explained; I don't believe it's a violation of the law to not do so.