On page SEO"3"

Heading Tags"H1, H2, H3", appear above paragraphs on a web page to

describe what the paragraph is about.

It also help the search engines to understand, what the web page is about, it is very important to both your web site visitors and search engines.

With out heading tags it is hardly for your web site visitors to read the content of your web page.
You should place the most important keyword in H1 header tag.

The second important keyword should be placed in H2 header tag.

Keywords in the first paragraph
first paragraph is very important on your web page , You should use the targeted keyphrase in the first paragraph, and also use it more than one time.

The first paragraph should be closed to H1 header tag.

Each web page of your site must have one paragraph of text at least.