(#) Heading 1 (Title)
(##) Heading 2
(###) Heading 3
(####) Heading 4
(#####) Heading 5
(######) Heading 6

Normally your post title is heading 1. And you can use heading 2-6 in the body according to your post. Headers help readers and search engines understand what the page is about and various parts of the content.