Heading tags (not to be confused with the HTML tag or HTTP headers) are used to present structure on the page to users. There are six sizes of heading tags, beginning with h1, the most important, and ending with h6, the least important.
Since heading tags typically make text contained in them larger than normal text on the page, this is a visual cue to users that this text is important and could help them understand something about the type of content underneath the heading text. Multiple heading sizes used in order create a hierarchical structure for your content, making it easier for users to navigate through your document.
Good practices for heading tags
Imagine you're writing an outline - Similar to writing an outline for a large paper, put some thought into what the main points and sub-points of the content on the page will be and decide where to use heading tags appropriately.
• placing text in heading tags that wouldn't be helpful in defining the structure of the page
• using heading tags where other tags like and may be more appropriate
• erratically moving from one heading tag size to another
Use headings sparingly across the page - Use heading tags where it makes sense. Too
many heading tags on a page can make it hard for users to scan the content and determine
where one topic ends and another begins.
• excessively using heading tags throughout the page
• putting all of the page's text into a heading tag
• using heading tags only for styling text and not presenting structure