This is an extra section of content organised into accordion format for easy browsing. Any number of sections can be added and customised per product, and set in any order, making for a highly flexible feature.
Alternatively you can use tabs, rather than accordion sections - you can change this on the Shop settings page under the "Product details page" tab.
You can include any kind of content in here, including rich content such as pictures and video.
To see how this works from behind the scenes, log in to the demo admin account using the floating button and go to Apps > Shop > Manage products > Tools > Edit the "Wood tamper" product > view the "Description" tab. This feature is included in the Advanced plan, but is also available as an add-on for the Ecommerce plan.