(h1, h2, h3, etc) – Header tags are used in HTML for categorizing text headings on a web page. They are, in essence, the titles and major topics of a web page and help indicate to readers and search engines what the page is about. Header tags use a cascading format where a page should have only one H1 (main title) but beneath can be multiple H2s (subtitles) and every H2 can have H3s beneath (sub-sub titles) and so on.
-H1 is used only once on a webpage, and is used to display the most important title.
-H2 is used to display the major subtopics of a certain webpage
-H3 is used to display the major subtopics underneath an H2 tag.