What does XML stand for?

XML stands for Extensible Markup Language. It is a flexible text format derived from SGML (Standard Generalized Markup Language) that is both machine-readable and human-readable. The term "extensible" is key, as it refers to XML’s ability to define custom tags, allowing users to create a structured format for data representation that meets their specific needs. This versatility makes XML widely used in data interchange between systems, web services, and configuration files.

The other options suggest variations of markup language definitions but do not accurately reflect the purpose and capabilities of XML. "Extended Markup Language" and "Executable Markup Language" imply functionality that does not pertain to XML's core characteristics, while "External Markup Language" inaccurately emphasizes externality rather than extensibility. Thus, the correct recognition of XML as Extensible Markup Language underscores its purpose in data formatting and exchange.