The HEADING tag is used to display your heading text in a larger font with <H1> being the largest down to <H6> being the smallest.
Some Search Engines place relevance on text displayed within the <H#> tags, so place some of your most relevant keywords within any of the 6 <Hx> tags.
|<H3>Your Guide to Health & Fitness</H3>|
Your Guide to Health & Fitness
When using the HEADING tags, you don't have to use the <H1> for your first heading. You may begin with the heading size of your choice. However, for your secondary headings, you should not use a larger heading than you began with. In other words, if you're using <H3> for your primary heading, then your secondary headings should be <H4> or <H5> and not <H1> or <H2>.