This feature play a critical role is the Listdom, you can add new fields for all categories or special categories and those fields will show in listings details that assigned to the related categories. For example for companies that are listing in your platform you want to have number of employees, in this case you can add this field in the companies category and whenever you want to add new listings in this category you will see this fields in the add listing page. And in the front-end when someone see that listing see the mentioned field as well.

Name: this is name or title of attribute that show in the front-end to end-users and back-end to admin users.
Field Type: this field specify the type of this attribute, for example text, number, email, URL, drop-down and separator
Each field type show special field in the add listing page.
Related categories: each attribute can assign to all categories, a group of categories or one category. With this way each category can have dedicated fields.
Index: this field specify the order of attributes. This is a float number and the higher numbers will show at the bottom of list.
Icon: this icon will show next to the attribute anywhere which that show.
Required: set this field is mandatory or optional.

Add listing view:

Front-end view: