Still not clear what schema markup is

Code on a page that tells search engines exactly what things are. Your page might say "4.8 stars from 120 reviews" as text. Schema labels that as a rating with a value and a count, so Google doesn't have to guess. Most people add it as a JSON-LD script or let a plugin like Yoast or Rank Math handle it. It doesn't push rankings up by itself. What it does is make the page eligible for rich results like review stars, product prices or event dates, and Google still decides whether to show them.