By default or if you hit cancel in the search field the words of the current Set are displayed. If you search (by word/reading or meaning), the app searches within all words of the program’s dictionary.

 switch beween:
Marking mode: if you click on a vocable it gets marked for your custom selection (Settings -> Test Set -> Marked Entries)
Detail mode: if you click on a vocable, details of this vocable are shown in the Practice View