What is structured data, and do I need it?
It is a block of machine-readable facts attached to a page, stating plainly what the page is about — a product, an article, a business, an event — and the details that go with it. It removes the guesswork that would otherwise stand between your content and an accurate summary of it.
What it actually is
Everything else on a page requires interpretation. A machine reading your contact page has to infer that a string of digits is a phone number and that the words above it are an address. Structured data skips the inference: it says, in a standard vocabulary, this is the telephone number, this is the opening time, this is the price. It sits in the page for machines and is never shown to visitors.
Why it matters
Two reasons, and the second is now the bigger one. It makes you eligible for the richer search results that take up more space and attract more attention. And it gives answer engines facts they can repeat with confidence rather than impressions they have to hedge. When an assistant is deciding whether to state your opening hours or say it is not sure, this is frequently what settles it.
What good looks like
At least one block of valid markup on each significant page, describing what that page actually is, using the standard vocabulary rather than an invented one. The facts in it match the facts a visitor can see on the page, and the type chosen reflects the page's real purpose rather than whatever was easiest to generate.
Being honest about it
This is not free and we will not pretend it is. It takes real effort to do properly and it produces nothing visible on your own site, which makes it easy to deprioritise and easy to do badly. It is also the single clearest way to be quoted accurately by machines, and that gap is widening. On a brochure site it is optional; on anything with products, locations, events or authored content it is close to essential.
Where most sites go wrong
The most common failure is markup that contradicts the page — a price in the structured data that no longer matches the price on screen, usually because one is maintained by hand and the other is not. Engines detect that mismatch and stop trusting the source. The second is generic typing, where everything on the site is declared as the broadest possible category, which is technically valid and conveys almost nothing.