AJAX : What is the difference between DOM Parser and AUX Parser?

In DOM parser is used at server side in php using domxml.
While AUX parser is used at client side in javascriptWhat is the back ground work going on when you type www.yahoo.com in your web browser?

actually there is nothing like yahoo.co.in it is actually an ip address which is resolved by DNS(domain name server ) so when you type yahoo.co.in this is the work of DNS to identify the pertucular page and redirect you to that page.
1. Browser gives a DNS request to the DNS server to resolve the name www.yahoo.co.in. The DNS request may be a TCP or UDP request to the DNS server.
2. After the IP address is recieved, the browser makes a socket connection with that IP Adress and port 80 ( if explicit port not given).
3. Now a Http GET request is fired by the browser on that socket connection and when the response starts coming it parses it and shows it on the screen.4. Note depending on the content of the first response , multiple sockets might be open to retrieve embedded images and objects in the same page.