<H# ...> indicates a header, a title of a section of the document. For example, to start the section of your page that discusses your hobbies, you might put
<H2>Header Tags</H2>
which gives us
Header Tags
there are six header tags:
H1
H2
H3
H4
H5
H6
Each header tag indicates the relative importance of each section it is heading:
<H1 ...> is for the major sections of your document, or as the one header to the entire document. <H2 ...> is for the secondary sections of your document, etc.
It's best to start with the highest level header (<H1 ...>) and work you way down.
So, for example, the headers in your page might look like this:
Headers are usually rendered so that the highest level are bigger and more prominent than the lower levels. All headers are rendered with a paragraph break before and after, so it is not necessary to use <P ...>. Don't use headers just to make text look bigger. This tends to look sloppy and falsely conveys the start of a new section.