The DataWeave Language is a powerful template engine that allows you to transform data to and from any kind of format (XML, CSV, JSON, Pojos, Maps, etc).
DataWeave is the MuleSoft expression language for accessing and transforming data that travels through a Mule app. DataWeave is tightly integrated with the Mule runtime engine, which runs the scripts and expressions in your Mule app.
DataWeave scripts act on data in the Mule event. Most commonly, you use it to access and transform data in the message payload. For example, after a component in your app retrieves data from one system, you can use DataWeave to modify and output selected fields in that data to a new data format, then use another component in your app to pass on that data to another system.
Full Reference
https://docs.mulesoft.com/mule-user-guide/v/3.7/dataweave-reference-documentation
