How spaced repetition works

Each rating decides when you see the card again. "Again" brings it back in the same session. "Hard", "Good", and "Easy" push it further out, a few days at first and then longer each time, up to about three months. Rating a card "Good" or "Easy" marks it mastered.

This works with the forgetting curve: reviewing a fact just before you would have forgotten it is the most efficient way to move it into long-term memory. Rate yourself honestly and the scheduler handles the rest.