Turn this into spaced-repetition cards

Material you need to retain long-term rather than just understand once.

Turn the material below into spaced-repetition cards.

Rules:
- One fact per card. Split anything compound.
- The front must be answerable from the front alone, with no ambiguity about what is being asked.
- Prefer cards that ask why or when over cards that ask what. A card I can answer by pattern-matching teaches nothing.
- Include cloze deletions only where the surrounding sentence gives real context.
- Avoid cards whose answer is a list of more than three items. Break those up.
- Add a few cards that reverse the direction: given the definition, name the concept.

Output as "Front | Back", one per line, grouped by subtopic. Aim for coverage of what matters, not one card per sentence.

Material:

Planning and retention. Working out the order to learn a subject in, and making it stick once you have.