Structured data is code added to a page, usually as JSON-LD using the schema.org vocabulary, that describes what the page contains in a form machines can read: a product, an article, an FAQ, a review.
Search engines use it to understand a page and may show rich results, such as ratings or breadcrumbs, when it's present and accurate.
It must match what's visible on the page. Marking up content that isn't there can lead to it being ignored.
Why it matters for a launch
It helps search engines and AI tools read your product's name, category, price and description correctly.