---
myst:
  html_meta:
    "description": "Why the Brazilian fields and widgets work the way they do: validation in two places, and values stored as digits."
    "property=og:description": "Why the Brazilian fields and widgets work the way they do: validation in two places, and values stored as digits."
    "property=og:title": "Concepts"
    "keywords": "Plone, Volto, plonegovbr.brfields, volto-brwidgets, concepts, explanation, validation"
---

(concepts-index)=

# Concepts

This part of the documentation explains why the packages work the way they do.
It's discursive rather than instructional; for directions toward a result, see {doc}`/how-to-guides/index`.

```{toctree}
:maxdepth: 1
:hidden: true

validation
```

`````{grid} 1 1 2 2
:gutter: 3

````{grid-item-card} Validation and formatting
:link: validation
:link-type: doc

Why the backend and the frontend each check a value, why the backend's check is the one that counts, and why a value is stored as digits.
+++
Start here.
````
`````

```{seealso}
The Diátaxis framework calls this class of documentation [explanation](https://diataxis.fr/explanation/).
```