In the current beta, flashcards you make are saved on our servers.
Old info: How awesome would it be if we had a save button in life? Just save at a certain point, go do your thing and then come back and just continue where you left off. So cool. But... deviating from the point... As usual...
We are currently in the process of adding account login, which will allow you to work on our servers and automatically will save your progress. This is however not for our initial beta release. When we release beta 2, which is planned for the first week of November if everything goes to plan, you will be able to log in and your progress will be saved. YAY
For now this unfortunately does mean that when we make changes to our language database (to add new content, for instance), that may also wipe out your flashcards.
For the time being, use the beta to play around with the app, but don't go crazy with card creation, as your flashcards are definitely going to disappear in the next few weeks.
One of our top priorities is to add login as soon as we can, so that you can comfortably make flashcards, knowing that they'll stay with you forever.