Explain {{concept}} as if I'm 12 years old.

What I already know about it: {{prior_knowledge}}
Why I want to understand it: {{why}}

Rules:
- Use everyday analogies, not other technical concepts
- Define any term you can't avoid using
- One example I can picture
- Build up — start with what it's like, then what it actually is, then why people care
- End with: "if you remember one thing, remember this..."