Content entity types and sub-types can have one or more <em>form modes</em>, used for editing. For instance, a content item could be edited in a compact format with only some fields editable, or a full format that allows all fields to be edited. In each form mode, each field can be hidden or displayed, and if it is displayed, you can choose and configure the <em>widget</em> that is used to edit the field. For instance, a taxonomy term reference field can be edited using a select list, radio buttons, or an autocomplete widget.