Headings are a great way of bringing attention to a particular section of your page, aswell as being a reliable and quick way to navigate a web site. The codes we use are, <H1-6> and </H1-6>...the numbers are for the different size of headings you can have (1 being the largest and 6 being the smallest). In the example above I've put 1-6 to show the headings available. If you were writing a heading 1, then you would type:
<H1>The title of your heading goes here.</H1>

and if you were typing a level 6 heading, then it would be:
<H6>The title of your heading goes here.</H6>

See below examples of all 6 levels of headings you can have:

This is a level 1 heading.

This is a level 2 heading.

This is a level 3 heading.

This is a level 4 heading.

This is a level 5 heading.

This is a level 6 heading.