Each theme uses Shopify's Product recommendations feature to suggest similar products to customers, based on the products they browse and other relevant data.
Activate product recommendations
To activate this, navigate to the theme editor, then open a product page in the right-side preview. In the left-side settings, open Product recommendations and enable Show dynamic recommendations.
Customize the copy for the Heading using the provided field.
For more information on how the Product recommendations feature works, read Shopify's article on its recommendation logic.