H1 - Let's Learn About Headings

H2 - The start of a section

Notice how the headings go down in logical order?

H3 - A sub-section of the above section

You def wouldn't want to jump to an H5 after this, for example. But you can use the same-level headings just fine.

H3 - Another sub-section of the same section

If you want a different sized heading but you're still in the flow of the same content, that's okay; that's what CSS is for. Changing font size via CSS won't affect accessibility.

H4 - A sub-header of the above sub-section!

See! That's a bigger header than the h3, but it's still an h4!

H2 - The start of an entirely new section

When you're done with the previous segment of content, it is okay to jump back UP in your heading tags.