This tag is used for 'most important title' .

This tag is for 'important titles' and can be used for the title of any new paragraphs.

This tag is almost the same, and is used for 'subtitles' more commonly.

This tag is for titles which are 'less important'.

This tag is for titles which are 'not important'.

And finally this one is for titles which are 'not important at all'.