The definition
Structured data is a standardised way of stating facts about a page so a machine can read them without interpreting prose. Schema markup is the vocabulary most commonly used, usually implemented as JSON-LD.
For a local business the relevant types are Organization or LocalBusiness, plus things like Service, FAQPage and Review where they apply.
What it does and does not do
It helps an engine read facts reliably and can make a page eligible for richer result formats. It does not manufacture authority, and adding markup to a thin page does not make it a good page.
Its real value in the AI era is entity clarity: unambiguous, machine-readable statements of who you are, tied to properties you control.
The rule people break
Markup must match what is visible. Marking up reviews you do not display, services you do not offer, or an address you do not operate from is a machine-readable claim that contradicts your own page. That is worse than omitting the markup entirely.
Check it yourself
Run your key pages through a structured-data testing tool and read what it reports, rather than only whether it validates, but what facts you are actually asserting.
Then check each asserted fact against the visible page. Anything marked up but not shown is the problem to fix first.
See where you actually stand
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