As whimsicalism says, it's like Anki. You get the question and then the answer; if you remember the answer, the question won't be re-asked for a longer time, i

As whimsicalism says, it's like Anki. You get the question and then the answer; if you remember the answer, the question won't be re-asked for a longer time, if you don't, the question will be re-asked sooner. It appears (?) to be a sort of global tool---you embed your flashcards into the text you are writing and the reader gets asked your questions in addition to questions from the math book they read last week or last month.