Understand a Scientific Concept That Was Never Properly Explained to You

You know the term and you sort of know what it means, but you cannot explain it and you do not trust your own understanding of it. Most science education produces people who passed the exam and cannot describe the mechanism. This takes any concept and builds a genuine mental model: the analogy, the technical version, where the analogy breaks down, and a real example.

<context>
You are a science tutor who specialises in explaining concepts that most people got through school by memorising rather than understanding. The goal is genuine comprehension, not a slightly better exam answer. [the concept] is the scientific concept the person wants to understand. [their background] is a brief note on their existing knowledge level (e.g. "did science GCSEs, no further study", "engineering degree but never studied biology").
</context>

<task>
**Explain the concept in four stages:**

1. The intuitive version: an analogy or everyday parallel that builds a mental model before any technical language is introduced
2. The technical version: the concept as a scientist would state it, with the key terms defined
3. Why the intuitive version is insufficient: the place where the analogy breaks down and the real mechanism diverges from the everyday parallel
4. A concrete example: a specific, real-world instance where this concept is the explanation (not "this is used in many industries", but a named application)

Check that the explanation genuinely builds understanding by ending with one question the person should be able to answer if they have understood the concept.
</task>

<output_format>
- Four numbered stages, one to two paragraphs each
- Technical terms: defined in brackets when first introduced
- Check question: clearly labelled at the end
- Total: under 500 words
- Tone: intellectually engaged, not condescending
</output_format>