I had the same response, so i googled it. The home page that came up for the Anki application (https://apps.ankiweb.net) doesn't really explain what it is either (it has a lot of fluff about how its useful and where its useful, but no actual information on what it does and how it does it.) I had to go to the docs link and read a good way into the user manual to get a sense of what it actually does. Still I'm not 100% sure I know what it is and how it works. Ok, its a flash card app. There have been hundreds of those going back to at least the 80s. And before that people were writing on 3x5 cards for a very long time. How is this better or more useful that?
Anki specifically is a spaced repetition [0] [1] flashcards app, similar to supermemo.
When you review a card, you can mark it as "Again", "Hard", "Good", or "Easy". The new interval of a card will depend on the grade, so it might be like 1day -> 2days / 3days / 4days, and so on. "Again" resets the interval to 0, like a new card.
The documentation is "open source tier", because anki is open source. It should be better, I agree, but something something you get what you pay for. Anki is free on pc/mac and android, but not on ios.
As someone who has used it for the last 2.5 years, I can wholeheartedly recommend it. In fact, I've written at length about it [2]. However I think the manual is pretty good [3] (for anyone who's curious).
Feel free to ask if you have any specific questions.
It's not just a plain old flashcard app, the point is to implement a scheduled recall system to help you memorize the content effectively while minimizing effort.
Anecdotally, it's also a lot more engaging than your average flashcard app. Using Anki feels like playing a video game, except that you also get quite valuable results out of it.
