what does the arguments of startelement() method in SAX parser refer to

Nav picture Nav · Apr 15, 2012 · Viewed 10.1k times · Source
public void startElement(String uri, String localName, String qName,
            Attributes attributes)

can anybody please give a simple example as to how localname is different from qName and what exactly is the uri string ? And yes before somebody asks I did check it on the net but no one cared to mention the difference as some examples used qName and others used localname which is really confusing for me.