Explain How Memory Consolidation Works While You Sleep

The reason you remember things better after sleeping on them is not a metaphor; there is a process. This explains what the brain is doing during sleep that helps memories stick, why cramming is less effective than it feels, and what one bad night's sleep after learning does to retention. Then one practical change.

Explain how the brain consolidates memories during sleep in plain language.

Cover:
1. What is happening in the brain during sleep that is related to memory (one paragraph, no technical neuroanatomy required)
2. Why cramming the night before an exam is less effective than spaced learning over several days
3. What happens to a skill or knowledge if you learn it and then have a poor night's sleep immediately after
4. One practical change to a study or learning routine based on this

Aim at a curious sixteen-year-old. Under 200 words.