The term "h1" refers to the HTML tag used to define the most important heading on a webpage. It is a key element in web design and search engine optimization (SEO), as it helps search engines understand the main topic of the page. Typically, there should be only one h1 tag per page to maintain clarity and hierarchy in content structure. In addition to its role in SEO, the h1 tag also enhances user experience by providing a clear and concise title for the content. It is often styled to stand out, making it easier for readers to identify the primary subject of the page. Proper use of the h1 tag contributes to better organization and readability of web content.