Practical explanation:
Search engines read text, but they don't always know what that text means in context. Schema markup gives them explicit signals — telling Google that a number on your page is a price, that a block of text is a review, or that a date is an event. That context helps Google decide how to present your page in search results.
In practical terms, schema markup is what makes rich snippets possible — the star ratings, FAQs, and product details that appear directly in Google's results page. Without the markup, Google has to guess. With it, you're telling Google exactly what's there.

How it works
Schema markup is added to your page's HTML using a standardised vocabulary from schema.org. It doesn't change how the page looks to visitors — it's invisible to them. It only affects how search engines read and interpret the page.
Diligently includes schema markup as part of its advanced on-page SEO setup, available in the Large website package and the Professional SEO Audit.
What to watch out for
Adding schema markup doesn't guarantee richer search results. Google decides whether to use it. Incorrect or misleading markup can lead to a manual penalty, so it needs to be implemented accurately.
Related terms: Rich Snippets, SERP Features, Technical SEO, SEO Audit