There are six levels of headings in HTML specified by H1, H2, H3 and so on. H1 headings are the most important and should be used as main headings, followed by H2 sub-headings, then less important H3 headings, and so on.
H1 headings help indicate the key topic of your page to search engines. You should generally have just one H1 heading. H2 headings help describe the sub-topics of your web page to search engines.
The above example shows how these headings might be used on a web page about kayaking. The style of each heading (font size, color, decoration, and so on) can be customized using a style sheet.