Hey Carsten;
A collection can be a set of articles, it could be all the articles for the current year (2015) in one collection.
When you want to make a new set of articles for the new year (2016) you can make a new collection, and put the new articles into this 2016 collection.
-- To make a new collection, Click on Collections in the "rail" on the left of the interface, then click New at the top...
-- -- Then you can add articles to that collection.
-- -- If you put this new 2016 collection in the top-level (default) collection, then the 2016 collection will appear on the app menu.
Keep in mind that you build new collections and add content to a collections by using Collections.
You build new articles and banners in Content.
I think we're updating the portal this week and I think this will include a new feature that makes this basic organization easier.
About "Products & subscriptions" -- this area of the portal is where you can create new product IDs -- these are a form of metadata for a collection.
Product IDs are used for identifying a collection in a store, you set pricing for a product ID. They're also used with restricted collections to require sign in to gain access to a particular collection.
You don't build a new collection through products & subscriptions.
HTH -- Colin