Certain fields can be displayed into the registration form. Not all fields can be added to registration forms, and specific fields (e.g email) will always need to be displayed.
In your dashboard, navigate to Users -> Registration forms and click the “Customize fields” link within the forms.
A new page will load with a drag and drop editor for the fields.
To add fields to a form, drag them from the left side, and drop them into the allocated area on the right side of the screen.
Each form can also have a specific user role assigned. The assigned role, will then be given to the user that registers through that specific form.