HTML is the main markup language used to create web pages and display information in web browsers. It uses tags (<tag>text</tag>) to structure documents and describe their nature. Key points about HTML include: - It stands for Hypertext Markup Language and is used to structure documents with hyperlinks to other texts. - HTML pages are written as plain text files that use tags to describe text formatting and structure. The files end with .html. - Web browsers are used to open and display HTML files, interpreting the tags and displaying the structured content.