XHTML, or Extensible Hypertext Markup Language, is a web markup language that blends the flexibility of HTML with the strict syntax rules of XML. Designed to improve web document structure and compatibility, XHTML ensures that web pages are more consistently rendered across different browsers and devices. Unlike traditional HTML, XHTML requires elements to be properly nested, closed, and written in lowercase, making it easier for machines to parse and process. This standard is widely used for creating web content that is both human-readable and machine-friendly.