Structure an explainer in layers

Layered explanation

Give the whole idea in its simplest honest form, then add depth in steps. Each layer works alone and the next one refines it. This follows the habit behind the Feynman technique (explain it simply, then notice where the simple version breaks) and the "explain at five levels" style of teaching. If you have not chosen a format yet, start with the explainer skill.

The layers

1. One sentence. What it is and why it matters, with no jargon. A smart reader who knows nothing about the field should get it.
2. One paragraph. The mechanism in plain words, with one concrete example.
3. The detail. The terms, the parts, the numbers, the exceptions. Define each term where it first appears.
4. The edges. What the simple version leaves out, where it breaks, and where to read more.

A short explainer can stop at layer 2. Most go to layer 3. Layer 4 is optional and best kept in an expandable section.

Template

In one sentence: <What it is and why it matters.>
In a paragraph:  <How it works, in plain words, with one example.>
In detail:       <The parts, the terms and the numbers, one idea per section.>
At the edges:    <What the simple version hides, and where it breaks.>

Example, for compound interest:

• Sentence: Compound interest means you earn interest on the interest you already earned.
• Paragraph: Put 100 in an account paying 5%: after a year you have 105, and the next year's 5% is paid on 105, not on 100. The gap with simple interest looks small at first and gets large over decades.
• Detail: the formula, a table of years, the effect of the compounding period.
• Edges: taxes, fees and changing rates.

How to write it

1. Write the one-sentence layer first and test it on someone who does not know the field, or imagine one. If it needs a defined term, it is not simple enough.
2. Choose one example and use it through all the layers, so the reader does not meet a new case at each level.
3. Introduce each new term with a definition at the layer where it first matters, not before.
4. Mark each layer clearly (a heading or a phrase like "In more detail") so readers can find their depth.
5. Check the layers do not contradict: a deeper layer may refine or qualify, but not reverse the simpler one. If it does, the simple version was wrong.

Pair it with a format

• Page furniture fits closely: a summary box for the first layer, define terms for the second, details sections for the deepest layers.
• An annotated walkthrough is the detail layer for anything that has parts: say the whole in a sentence, then walk through the parts.
• In scrollytelling the layers become steps: each step adds one layer to the same visual. Keep it to three or four.
• For the decision a reader must make, Answer first is better, because layers teach and do not persuade. For the mechanism behind the idea, How it works.
• Math belongs in the detail layer. See math-and-code-blocks.

Mistakes

• A first layer that is a definition full of terms ("an asset-liability matching instrument...").
• Changing examples at every layer.
• Making the simple layer wrong to keep it simple. Simplify, but do not say false things.
• Putting every exception in layer 3. Exceptions go in the edges.