HTML, or Hypertext Markup Language, is the backbone of web development. It provides the structural foundation for creating web pages by defining the elements on a page such as headings, paragraphs, links, images, and more. HTML uses a system of tags to organize content and give it meaning.

CSS, or Cascading Style Sheets, is the styling language that brings life and visual appeal to HTML content. While HTML defines the structure, CSS controls the presentation and layout of web pages.