Final answer:
The tag is used in HTML for the most important heading, while the tag is for the smallest heading.
Step-by-step explanation:
The <h1> tag in HTML is used for defining the most important heading of a webpage, often the main page title or a major section heading. It is typically displayed in the largest font and used to introduce the main content, setting the tone and theme of the website.
For the smallest heading, the <h6> tag is used in HTML. This tag defines the least significant headings on the page, and text under this tag is shown visually smaller than other larger headings like <h1> through <h5> tags.