JAXP is an XML framework by SUN that allows programmers to plug-in any W3C compliant XML parser using Java's system property files. It is not a parser by itself, but provides a level of abstraction by facilitating dynamic parser selection.
JDOM is another XML framework that integrates standard Java collection classes with any W3C compliant DOM parser allowing programmers to manipulate DOM objects as Java Collections. Very much like JAXP, JDOM sits between the application and the parser. Note that JDOM by itself is not an XML parser
Xerces is Apache's collection of software libraries for parsing, validating, serializing and manipulating XML. The library implements a number of standard APIs for XML parsing, including DOM, SAX and SAX2.
dom4j is an easy to use, open source library for working with XML, XPath and XSLT on the Java platform using the Java Collections Framework and with full support for DOM, SAX and JAXP.
these are above lines which are putting me in confusion on JAXP.
On DOM and SAX ,from the above i understood that they are standard APIs.