All HTML documents must start with a document type declaration:<!DOCTYPE html>.
The HTML document itself begins with <html> and ends with </html>.
Most HTML elements have an opening tag <tagname> and a closing tag </tagname>.
HTML provides the basic structure of a web page. This includes elements like headings,paragraphs, links, images, lists, tables, and forms.
The two most used extensions of HTML documents are . html and . htm.