Ankidroid is a flash cards app that I have probably used the most for my NEET PG preparation. For those who are not familiar with flashcards, a flashcard is a card bearing information, as words or numbers, on either or both sides, used for revising and memorizing. One writes a question on one side and an answer overleaf. There are a lot of flashcard apps available in the play store and you can use any of them. Now this app is based on the principle of spaced repetition for revision. You can make your own flashcards in the app(so this app is of better use if you start a bit early). These flashcards are then repeated in the app on particular time intervals.