# Concepts

What PowderLine does, and why it works the way it does.

| Page | Read it to understand |
|---|---|
| [How PowderLine works](how-powderline-works.md) | The whole picture: recipe, validation, engines, results, provenance |
| [Recipes](recipes.md) | What a recipe holds, and why engines are never mixed |
| [Validation](validation.md) | What is checked before a run, and why so strictly |
| [Results](results.md) | Uniform statistics, the output recipe, provenance, failures |
| [Good refinement practice](refinement-practice.md) | Rules of thumb, and what PowderLine does *not* judge |
| [Comparing engines](comparing-engines.md) | The same data in every engine, and why the numbers differ |

```{toctree}
:hidden:

how-powderline-works
recipes
validation
results
refinement-practice
comparing-engines
```