Product tabs is only available in Product templates. Once you navigate to Product template you will immediately notice the section:
This section is mainly to display Product description but you can display:
Specifications
Pros and Cons
Product recommendations
Content tab in which you can add custom content (html/liquid/page and image)
Product description:
For displaying Product description in product tab > simply click on add block and click on product description.
Specifications:
In the following video tutorial you can see how you can Specifications using metafields in Xpert theme.
Pros & Cons:
Here's a video on how you can setup Pros and cons in Xpert.
Product Recommendations:
You can add Product recommendation section as a tab.
Custom tabs:
For adding custom tabs just add the content tab blocks:
