SharePoint 2013 Tags vs Keywords

I am trying to figure out how tags, terms and keywords are should be used in SharePoint 2013.

I have read a lot of articles about it and think that I understand the differences between these types.

But there are still things unclear to me: I have enabled the enterprise keyswords column in a document library. When I upload a File, I can edit its properties and enter keywords. And then there is the Tags & Notes button in the Ribbon. When the item has keywords in the taxkeyword column the Tags & Notes window does not show these keywords. Why is there a difference? Both fields can be edited by the users, right?

Thanks in advance.

best regards Alex