Anki is a cross platform program for learning using spaced repetitions. It uses a “flash card” system with sophisticated scheduling so you can learn each card the minimal number of times that it takes to memorize it. The basic principle is that it shows you the “front” of a card. It can be a definition to a word (or the reverse), a picture, a question or all together. After you decide on what you think the “back” of the card is, you click on a “show answer” button. Then you tell Anki if you were right or not. You can use Anki to learn anything - languages, math, science, music, etc.
This is a companion discussion topic for the original entry at https://amir.rachum.com/blog/2016/10/19/learning-a-language-with-anki/