markup is code (semantic vocabulary) that you put on your website to help the search engines -like Google- return more informative results for users. So, Schema is not just for SEO reasons, it’s also for the benefit of the searcher.

In fact, Google, Yahoo, and Bing partnered to create vocabulary. This effort comes to help developers implement markup into websites to enhance the overall search experience.

Google recommend you add new structured data markup with JSON-LD, separate from your HTML markup, especially if your product data contains variants. Added markup are distinct from any user-facing code, which makes it easier to maintain. Any structured data markup specifically designed for Google usage can be added without changing any of the visual elements of your site. Note that the code that generates your structured data needs to be kept in sync any changes to the user-facing elements on your site.

Google: Add new structured data markup (recommended)