Documentation:
Simple Heading

Here you can control the module’s size.

Fullwidth

Here you can set the element’s width. Set this to OFF to have the element wrap to the width of its text. Set this to ON to have the element extend the fullwidth of its parent element.

See here for an example.

Other settings here are common to most Divi modules and are not discussed further. For more information on common Divi module settings, please consult the Elegant Themes Documentation.