Extensible Markup Language (XML) is a flexible, self-descriptive language for encoding information in a format that is both human-readable and machine-readable. Coursera's XML catalogue teaches you the fundamental principles of XML, including its syntax, rules, and guidelines used for defining, validating, and sharing document formats on the web. You'll learn how to create well-formed XML documents, manipulate XML data structures, and parse XML for data extraction. Additionally, you will dive into advanced topics like XML namespaces, Schema, XPath, and XSLT. These skills are essential for roles such as web developer, software engineer, data analyst, and other IT professionals aiming to enhance their expertise in web technology and data interchange formats.