Search Preferences 

Search by Name - Enable searching by item name by typing in the search box.

Search by Code - Enable searching by item code by typing in the search box.

Search by Description - Enable searching by item description by typing in the search box.

Search by Category Name - Enable searching by item category name by typing in the search box.

Custom field Search - Each custom field is searchable using this toggle, e.g. brand names used as item custom field. In the image above, 'text field' and 'dropdown field' are custom fields.