Against each item you can assign a label of your choice from the list of labels.
There are 6 types of labels:
While adding any Articles, Videos, Twitter posts, embed link or any kind of item by default they will be labeled as 'General' . You can update them just after adding an item or afterwards from Edit section.
According to your research need or working pattern you can use labels against you basketed items.
The items you will assign under 'Secret' will not appear in any listing or inside normal search results. Those items will come exclusively if you Search for them by label from the search section.