(Extensible Markup Language) is a markup language similar to HTML, but without predefined tags to use. Instead, you define your own tags designed specifically for your needs. This is a powerful way to store data in a format that can be stored, searched, and shared. Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The World Wide Web Consortium's XML 1.0 Specification of 1998[3] and several other related specifications all of them free open standards—define XML. This course is dedicated to learn the basic Theoretical conceptsof XQuery.XQuery is thelanguage for querying XML data .XQuery for XML is like SQL for database. itis built on XPath expressions. XQuery helps in queryingdata fromXML whichplays an important role in many IT systems. For this reason, it is important for all webdevelopers to have a good understanding of XQuery. Before you continue, you should also have a basic understanding of XML,XSLT,XPATH,HTMLand Javascript . in this course you will learn the theoretical concepts of basics of XQuery. this is a beginners level course and this course is not for experts in XQuery