XHTML stands for Extensible HyperText Markup Language. It is a markup language that combines the syntax of HTML with the strict structuring rules of XML. Developed by the World Wide Web Consortium (W3C), XHTML was created to make web pages more standardized, easier to parse, and capable of working seamlessly across a wider variety of devices, including desktop computers, mobile phones, and other internet-connected hardware. Because it adheres to strict XML standards, XHTML documents must be well-formed, meaning all tags must be properly nested, correctly closed, and written in lowercase. This strictness eliminates the ambiguity that often plagues traditional HTML rendering in different web browsers. Although HTML5 has largely superseded XHTML for modern web development by adopting a more forgiving parsing model while still supporting XML-like syntax, XHTML files are still widely used in legacy web applications, EPUB e-books, and specific enterprise environments where strict data validation and automated processing of web content are strictly required.