Why headings matter for SEO
Headings tell visitors and search engines how a page is organized. The H1 is the page's main heading; H2s are the main sections; H3s sit inside H2s, and so on.
A clear outline helps Google understand which parts of the page answer which questions, and helps visitors skim to what they need.
Good heading structure
Use exactly one H1 that says what the page is about. Then go one level at a time: an H3 should sit under an H2, not straight under the H1. Don't use headings just to make text big; use CSS for that.
Write headings people would search for, like "How to convert STL to STEP" instead of "Step 2".