The H1 heading tag is the name/title of your page or post. It has a class assigned to it that cannot be replicated here within the blog post – solely in the title. It should be unique, succinct, and clear. Each page should only contain one H1 heading.
This is your H2 Tag
This denotes the first section (like chapters of a book). You can have multiple H2 tags to indicate different sections. It is strange that this tag is both centered and smaller than your H3 tag.
In this post, to give it definition, I placed two horizontal dividers above and below the H2 Tag.
This is your H3 Tag
This should fall beneath an H2 tag for clear hierarchy, but it is literally just a sub-subheading and not terribly significant beyond the structure.
This is your H4 Tag
As you can see, this is no different from your H3 tag, so I likely won’t use it when posting as it serves no purpose. Usually, I can satisfy this with a BOLD version of the font, but this font doesn’t show up in BOLD as any different, so it’s not really functional.