SEO H1
An H1 Tag is a Heading Tag. Heading tags are used as a heading title for a page. Heading tags start at an H1 and go down to an H6 tag. For example, the heading of this page where it says SEO H1 is an H1 heading tag. The next heading below is an H2 Heading Tag.
Why Use Heading Tags?
Heading Tags are an important on-page seo factor. It is important to define to a web browser and a search engine what certain aspects of your page mean.
It is possible to just simply style your whole site with span tags but this is not symantically correct code and is not very search engine friendly.
Correct Use of H1 Tags
An H1 tag should be used once and once only per page. The opening heading should be an H1 tag that describes the whole theme of the page. Any sub information or more specific topics should go under seperate headings in the form of H2 Tags, filtering down appropriately.