XML, or Extensible Markup Language, is a markup language that defines a set of rules for encoding documents in a format readable by both humans and machines. Born as a simplified subset of the Standard Generalized Markup Language (SGML), XML's primary purpose is to facilitate the sharing of data across different systems, particularly systems connected via the internet. Unlike HTML, which is used to display and format content, XML focuses on describing the content's structure. This descriptive nature allows XML to be utilized in a plethora of applications, from simple data storage to complex configurations and data exchange protocols. Each XML document consists of elements, attributes, and text, defined using opening and closing tags. To ensure that an XML document adheres to a specific structure, XML schemas (like DTD or XSD) can be used to describe and validate the content of XML files. XML's platform-independent nature ensures that it remains one of the preferred choices for data interchange. Whether in web services (like SOAP), configuration files, or even document storage (as seen in Microsoft's Office Open XML format for Office documents), XML's versatility shines. Over time, XML has birthed a variety of related technologies. XSLT, for instance, is a language for transforming XML documents. XPath, on the other hand, allows querying of XML files. XML namespaces ensure that XML documents remain unique, preventing potential conflicts in tag names and attribute names. In an era where data interchange is paramount, XML plays a crucial role in ensuring that data remains structured, interpretable, and most importantly, exchangeable. Its adaptability and wide adoption in various technological domains underscore its continued relevance in the digital age.