Display Field option for a lookup field in the Lookup Configuration dialog box allows you to specify the field value that should be displayed for that field in the SFM Delivery screen. By default, it is set to the Name field of the object.

For example, for a Product lookup field, if you wish to display the Product ID instead of the Product Name, the Display Field should be set to Product ID in the corresponding lookup configuration. On the SFM delivery screen, the Product ID will be displayed as the value of the Product field instead of the Product Name.