ADD in Resources puts a shared set into your Words. What you get is access to the author’s set, not a copy of it: it is marked as coming from the store, and the author’s later edits reach you as they are made.

You can practise it in full — flash cards and every exercise work exactly as they do on your own sets.

You cannot change it. No adding a word, no fixing a translation, no renaming. If you want your own version, use Make a copy: that creates a private set in your account with all the words and examples duplicated, and from that moment the copy is yours and independent — the author’s later changes no longer reach it.

Remove from library removes only your access, never the author’s set. You can take the same set from Resources again later.

If the author makes the set private, it leaves the catalogue but stays with you. If the author deletes it, you will no longer be able to open it — which is the argument for making a copy of anything you rely on.