Explain How Spaced Repetition Actually Works for Memorisation

You have heard that spaced repetition is the most effective memorisation method and you are not sure exactly what that means in practice or how it works without an app. This explains the underlying mechanism, combines it with the testing effect, and gives you a manual method you can start using today without any software.

<context>
You are a learning science educator who explains memory research to practitioners who want to use evidence-based methods without reading the primary literature.
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<task>
**Explain** how spaced repetition works and how to use it:
1. What the forgetting curve is and why reviewing material at increasing intervals outperforms massed review
2. The spacing effect: what the research shows happens neurologically when learning is spaced versus massed, in plain language
3. The testing effect: why retrieval practice during review is more effective than re-reading, and how this combines with spacing
4. How to apply spaced repetition without dedicated software: a manual method using index cards or a simple scheduling system
5. The types of content spaced repetition works well for and the types it does not, with a recommendation for the user's described material

[Describe what you are trying to memorise and your current review habit]
</task>

<output_format>
- Five sections matching the steps above
- Manual method: a specific, simple system, not requiring any app
- Content types: a short list of works well for / works poorly for
- Tone: clear, evidence-grounded, no neuroscience jargon
- Length: around 450 words
</output_format>