Take a look at the screen shot of the Blue Ink Web services page for a visual example. The tags breakdown as follows:
<H1> Lead Generating Services </H1>
<H2> Here's what we've got to offer </H2>
<H3> Website design & development </H3>
<H3> Content development </H3>
<H3> Social Media </H3>
The H1 tag indicates what the page will be about, lead generating services. The H2 tag supports the H1 tag, and the H3 tags are used as subtags of our H2 tag.
Websites that do not have or properly use H1, H2, H3 tags, etc, will be hurt in search engine rankings.
If you're looking for SEO, website design or digital marketing help, contact Blue Ink Web to discuss your project.