Anki is a spaced repetition software (SRS) for flashcards. The better explanation can be found on the project’s website.
In general, Anki takes the concept of spaced repetition in the form of decks and flash cards and it shows them to you in a specific order to help you memorize them.
As long as you keep using Anki every day, you will be able to remember the information that is being shown to you.
Most people among thelearning community use it to learn various things, mostly vocabulary and kanji (although it can also be used to train listening comprehension or practice on grammar points as well).
There are a lot of decks (i.e. collection of cards) made by others that can be downloaded and added, and this is the most popular option for beginners. They can be found directly on the official website.
The real strength of Anki, however, is in being able to make your own decks from scratch. I briefly touch on this in mypost.
Downside of Anki
By default, Anki has pretty terrible settings which can (and most likely will) lead to burn out and regrets and you’ll start to hate the software. They can be extremely merciless, especially if you skip a couple of days or more of reviews and they start piling up quickly.
This is why I recommendto make the experience worthwhile.