HTML & CSS are languages used to structure and style web pages. HTML provides the content structure using elements, tags, and attributes. CSS controls the style and layout using selectors, properties, and values. Some common HTML terms include elements, tags, and attributes. A basic HTML document structure includes DOCTYPE, html, head, title, and body tags. CSS can be used to style HTML elements by selecting them with tags, classes, IDs and applying properties like color, font-size, background, and more.