Spaced repetition, also known as spaced revision, is a technique used to overcome the 'Forgetting Curve'. The Forgetting Curve is a theory proposed by Psychologist Hermann Ebbinghaus that states humans forget information over time when there is no effort made to retain this information; the longer you leave it, the less you will remember. Spaced repetition is a technique used to enhance long-term memory retention by strategically spacing out review sessions, rather than reviewing everything at once. The core idea is to revisit information just before you're about to forget it, which strengthens the memory trace and makes recall easier over time.
The 2357 method is a type of spaced repetition where you review a topic at increasingly longer intervals. It works by studying something just before you're most likely to forget it. You can use it as a useful tool to plan in revision sessions before an exam, as illustrated below.