On-page SEO refers to the practice of optimizing individual web pages to rank higher and earn more relevant traffic in search engines. It involves both the content and the HTML source code of a page (as opposed to off-page SEO which deals with external signals like backlinks). Key elements of on-page SEO include optimizing title tags, content, internal links, and URLs; ensuring good keyword placement and density; improving site speed and mobile-friendliness; and ensuring the page is structured and tagged correctly for search engine crawlers. This practice not only makes it easier for search engines to index and understand the content of a page, but also enhances the user experience, increasing the likelihood of keeping visitors engaged and converting them into customers.