How our search system works.
You can add some default search fields from WP > Classiads options > listing settings > search settings
here you can turn options ON/OFF. set the width. And these will affect on archive form as well.
Secondly you can add content fields. Go to WP > Classiads options > content fields
Every content field have options to add this content field in the search form. A normal and advance as well. You have options to add in custom form, archive form and widget form.
Custom form are which you have in the pages like home page. an element “Search Form” available in the shortcodes. If you add this element in any page. that search will be a custom search and will work globally. Means whatever you will add in this form will affect all the custom search forms.
Archive form are which you can see when you hit a search on the home page and it gives you a result page along with search. This search form called. Archive search.
The search form you can see in the side bar or in the footer are called Widget form. as these can be active from WP > Appearance > widgets
In every content field you have options to add this content field into the advance search form. If you select the box for advance then it will show only when you open the advance search or if you have selective category. You will click on the category the related content fields will be open in the advance section.