Although it appears to be a page, a web form is technically a SharePoint site that uses a specific template. Each form site has three elements: the form web page, the confirmation page, and a responses list.
You cannot add any additional elements/pages/sites to a forms site, nor can you delete any. The form site template is pre-packaged with the form page, confirmation page, and responses list and it cannot be modified. The simplicity of the form site elements is what enables users of all technical knowledge levels to effectively create and manage forms.
Form web page
The form web page is the actual form – the page that displays the questions you need to ask your users. This page uses a web part to pull in the form questions developed by the website owner/editor via a SharePoint list. You can edit and select the questions you want displayed on the page, and you can also add text and images to the form web page if applicable.
The form web page is only used to display the form. You manage all form questions and data received via submissions using the Responses List.
The web form page is one of two pages in the Pages folder of the form site, and is named form(default). The page name can be edited to better suit your needs.
Here is an example of a form web page currently active: