[Theme: Olsen] Post Utilities and Secondary Image

I just bought a template called Olsen from Creative Market. I found a section on a post editor page called Post Utilities. There are two options: layout and secondary image.

Under secondary image it says, “The Looks page template uses images in portrait (tall) orientation. If the Featured Image of this post is in landscape (wide) orientation, you may want to provide a portrait image to be used instead, otherwise an automatically cropped image (based on the Featured Image) will be used.”

Uploading a secondary image does not affect the Featured Image. What is the secondary image for?