The markup language that gives every web page its structure and meaning.
HTML (HyperText Markup Language) is not a programming language — it's a markup language that describes the structure and meaning of content. The browser reads an HTML document, parses it into a tree of nodes called the DOM, and then renders that tree. Every page starts with a <!DOCTYPE html> declaration, which tells the browser to use standards mode instead of quirks mode, followed by an <html> root that contains a <head> (metadata, title, linked resources) and a <body> (what users actually see).
A common interview trap is treating HTML as forgiving syntax you can write carelessly. Browsers do recover from errors — an unclosed <p> or a missing <tbody> gets silently fixed — but the fixed result may not match what you intended, and different parsers can disagree on edge cases. Knowing the document skeleton, how the parser builds the DOM, and why the charset and viewport meta tags matter shows you understand what's happening before a single pixel is painted.
What you'll walk away knowing