# Validation rules

The purpose of a form is to validate the entered data. Unlike other solutions, where a developer is given a single `validate` function, React Advanced Form uses smart built-in validation algorithm based on the [Validation schema](https://redd.gitbook.io/react-advanced-form/validation/schema). It is a convenient functional way of declaring validation rules, from simple to complex. 

This part is going to focus on how to declare a validation schema and write the rules. We are going apply the validation rules and messages to the forms in the next part.

{% content-ref url="../validation/getting-started" %}
[getting-started](https://redd.gitbook.io/react-advanced-form/validation/getting-started)
{% endcontent-ref %}