Headlines are HTML elements that organize the content structure of each web page. They are typically broken down like so:
h1- The main topic of the page. You should only have one h1 tag.
h2- subheading of the h1. You can have multiple h2 tags.
h3- subheading of h2.
You don’t have to use every heading element on a page but it is good practice to structure your content with headings and subheadings. It’s mandatory for good SEO.