Product merging is the process of combining several products on the same page.
This allows you to create a product with different visuals (for example white text on black products and black text on white products) on the same product page.
This also allows you to combine certain products on the same page: you can create a "Mug" page with a particular design and propose the ceramic variant with the enamel variant.
Create first product
Create another one
Then, on top dashboard top menu click on "Products"
Click on "merge products".
Choose the products you want to merge
Choose the merge behavior
Final product on your webshop
Other example with 2 different mugs. Note, that in this case, a new "Product" dropdown appears with product name (you can edit the product name directly in Shopify by clicking on the variant name).
When you merge products, description will always be the "master product" description. Don't forget to edit it if needed.