About [[MediaWiki:Moodbar-action-item/en]]

I've not been able to see the message, but a feedback item is any single entry of Special:FeedbackDashboard[1] (mw:Feedback Dashboard). Perhaps it's used in some administration special page whose actions show on «the log of actions taken on feedback items listed on the feedback dashboard»

Just wondering what is the difference between feedback and feedback item.

The feedback is the initial content of the feedback item, which can also contain responses to feedback and whatnot? Dunno.