In our iOS app, you may have noticed a little ☆ icon it the top corner of the flashcard, and in the Card List for each Deck. We call this the "Bookmark".
People use Bookmarks to help them quickly access cards that they want to come back to later. For example, perhaps you want to mark all the flashcards that you think are going to be on your next quiz. Or perhaps you want to mark all the flashcards where you have questions, so you can remember to ask your teacher or tutor the next time you see them.
To bookmark a card, simply tap the ☆ icon, and it should turn a darker color. To un-bookmark it, tap the ☆ icon again.
You can easily access all your bookmarked cards by looking at the top of the Decks list for the particular Class, and tapping on the row that says Bookmarked Cards. This brings you into a Browse Mode experience for only the bookmarked flashcards in that Class.