HTML has evolved from version 1.0 in 1990 to the current version HTML5 released in 2014. It is a markup language used for web page structure and layout. HTML5 introduced many new semantic elements, form input types, and multimedia elements to improve accessibility and functionality on modern browsers. When constructing an HTML5 page, the doctype is no longer required, the charset should be declared, and new structural elements like <header>, <nav>, <section>, and <footer> can be used to represent different page sections semantically.