[jQuery] jQuery.AJAX statement

hi

I am very new to jQuery.  I am trying to make up a 'load on scroll'
function.
I have a few questions on the following piece of code.
-Is jQuery.ajax a valid call ? or should i be using some other module
beside jQuery?
-what does dataType: html mean? what other dataTypes could I be
returning?
-My biggest confusion is that when mycontent.php is called HOW can i
pass a variable to my php code, say 3, so that it can return values
from (25 * 3) onwards (assuming i want to load next 25 records each
time call to mycontent is made)?

I have gotten/modified this code from www.dzone.com.  I am trying to
implement their 'load on scroll' functionality.


           jQuery.ajax({
               type: "GET",
               dataType: "html",
               url: "www.mycontent.php",
               success: function( html ){
                   html = jQuery.trim( html );

                   if ( html )
                       jQuery("#content-inner").append( html );
                   else
                       curPage = 0;
               }
          });

I'd appreciate any help.