Tim Berners-Lee invented HTML at CERN to help share scientific documents. HTML uses tags to structure text and multimedia on web pages. The basic structure of an HTML document includes header (<head>) and body (<body>) sections. The <head> contains metadata like the <title>. The <body> holds the visible page content, and elements like <p> define paragraphs. HTML tags like <b> make text bold, while <img> embeds images. More advanced tags have been added to later HTML versions to support richer content and functionality on web pages.