Structured data helps Google better understand your site. With Structured data, you provide additional guidance, explicit clues about the meaning of a page to Google. From structured data, Google can provide better and richer results. Rich results go beyond the standard blue link and will improve the organic traffic click-through rate.
There are several types of rich results. Good Shopify themes will provide out-of-the-box good support but there is still room for improvement.
Structured data formats
JSON-LD is the recommended format by Google. It is added as a JavaScript notation embedded in a script tag. JSON-LD keeps your content and structured data separated, minimizing the risk of broken data structures. It makes it easier to nest items, has dynamic support, and will be much more maintainable.
Microdata/RDFa structured data within the HTML content. This makes nesting much harder as your data and content need to be in sync. Microdata is used on many Shopify themes and I've seen many cases where everything went wrong due to an HTML error. If you are using Microdata, you should update to JSON-LD.
Most used Rich Snippets
There are quite a few formats provided by Google but these are the most commune Rich Snippets used on Shopify:
Logos
Information about your organization. Besides the company logo and URL, you can add additional pieces of information such as an address, founding date and location, social profiles links (Facebook, Instagram, Twitter). Only logo image and URL are required but it is recommended to fill in the rest of the available fields. Usually Logos structured data is added on the homepage.
Sitelinks Search box
This Rich Snippet allows Google to display a search box, within the search results. This is a quick way for people to search your site. Usually the Sitelinks Search box structured data is added on your homepage.
Breadcrumb
The breadcrumb rich snippet indicates the page's position in the site hierarchy. Within Shopify, it makes sense to use this on products and blog posts/articles pages.
Article
It is the structured data suitable for blog posts/articles. The article data contains entries such as the article URL, image, published data, headline author, and article body.
Product
Probably the most important rich snippet on your Shopify store. The product structured data helps Google to provide rich snippets such as price, availability, and review ratings. Most of the data (images, pricing, availability, SKU, brand) can be pulled from the Liquid product object. Most review apps will output data, via metafields, that can be used to populate the reviews.
FAQ, HowTo, Recipes - Mix, and match, get creative with your rich snippets.
As mentioned there are several types of structured data/rich snippets provided by Google. You can add several to a page. Let's look at a product page. We can have the breadcrumb and product by default. Review apps will add the product review structured data. We can add an FAQ with a few questions/answers related to the product. Some products can benefit from a How To. A HowTo rich snippet can cover steps needed for a product assembly, cleaning, or maintenance.
Do you sell groceries? A recipe structured data can be added. These additional snippets will let Google display rich snippets and increase your organic listing visibility.