whats the difference between JAXP parser which comes with java1.4 and Xerces parser

I am using java 1.4

and using the dom parser:

import org.w3c.dom.*
and
import javax.xml.parsers.*



I also had xerces parser in my lib folder and I was getting error when trying to :

DocumentBuilder builder = factory.newDocumentBuilder();

but when i removed the serces.jar fiel from my lib folder it was working


question ) whats the difference between JAXP parser which comes with java1.4 and Xerces parser ??????????