Add Extra fields in User Form I want to add extra fields during user registration. I don't Understand Where I can access to user form and user twig, because I want to validate and reformat the Form.

My background is symfony, and I expect The model if I want to add some properties ( in drupal maybe is entity ) and the twig ( the view Parts ), Instead here I don't know where is the user form. 

I'm trying to create the module and use some hook, but I don't know if the right way to customize the form
You can go to configuration -&gt; account settings -&gt; manage fields and add your field. then in the settings check it to show in registration form

admin/config/people/accounts/fields