The form HTML element represents a document section containing interactive controls for submitting information. It is possible to use the :valid and :invalid CSS pseudo-classes to style a form element based on whether or not the elements inside the form are valid.
The fieldset HTML element is used to group several controls as well as labels within a web form. The legend HTML element represents a caption for the content of its parent fieldset.
The value of the for attribute must be a single id for a labelable form-related element in the same document as the label element. So, any given label element can be associated with only one form control
In this reference document it talks about how the form elements is done using Novalidate, method, action. seccondly fieldset and legend and lastly For and Id. All of this are part of form element attributes.