The importance of heading order
When selecting heading levels, ensure that they are in outline order. This will help the semantic structure of your page and assist those using non-visual devices. For example, a Heading 4 should only be a sub heading under Heading 3, not Heading 2.
The title of the page is considered Heading 1, which is edited through the Properties tab. The heading options within the toolbar are Heading 2- Heading 5 which is in order of largest heading to smallest.
Typically Heading 2s are used to section out the main points of the page - best practice is no more than two
Heading 3s can be bolded to look like a Heading 2; the screen reader it will read it has a Heading 3
Heading 3s can be though of as sub-topics or sub-categories to the Heading 2, then Headinf 4s and even more narrow sub-topic that further supports the Heading 2
Heading 3 normal
Heading 3 bolded
Heading 2 normal
Read more about headings