From the web site:
StAX is a standard XML processing API that allows you to stream XML data from and to your application. This StAX implementation is the standard pull parser implementation for JSR-173 specification.
http://stax.codehaus.org/
It is an alternative to the venerable SAX and is much more powerful and robust than TAX (see TAX Revisited for an upgraded version, TAX: A Tiny API for XML for the original).