Spaced Repetition
From Learn Any Language
(Also, SRS" either "Spaced Repetition System" for the idea, or "Spaced Repetition Software" for a program which implements it.)
For language learning, Pimsleur implements Spaced Repetition via prompting and review at intervals designed to maximize your retention. The idea is to remind you of the answer just as you were about to forget it.
Flash cards, either physical or software, are also generally used with a SRS.
