Can someone give a introduction of XmlSchema?

[Zhang zhongliang]

I know in the axis2 API,the AxisService has the method getXmlSchema() and 
getXmlSchema(int index),I do not know what is the XmlSchema's function?Is it a 
document tree of XML Schema object?Can I use it as a schema source to validate 
a well-formed xml file?

Thanks a lot for any advice.