Definition:

The heading element in HTML defines a structure for headings in a document. Starting with H1 as the most important heading, descending to H6, heading tags are a standard part of HTML. The H1 tag is the most important heading element on a web resource. Generally there should only be one H1 on a page, but it is not a major problem to use more than one if it helps to describe the content of a page ie, if there is more than one section on a page.