In this section, you can add all the Sort Functions that will be displayed on the top of the Search Results Page. In the first row when you click on Add New, 3 columns are to be filled for each Sort you want to add which are as follows.
Field: Here you can select the field of the sort. For e.g. Any Named Tags, Options, Metafields, Selling Price, Discounts, etc
Label: Have a custom name for the field you have chosen
Order: Ascending or Descending