var menuLinks = $('.menuLinkClass'); // now the variable 'menuLinks' is a jQuery object
var mainDiv = $('.yourMainDivClass'); // same here for 'mainDiv'

menuLinks.click(navigate) // menuLinks is a jQ object, so it has all of jQuery's methods, like .css(), .attr(), .load(), etc...

// most jQ methods and functions have whats called a callback. You often seen it written
// like this: $('.class').click(function(){ with code in here })
// but that is sloppy
// here I declare a variable, 'navigate', which 'points' to some function.
// Above, when a menuLink is clicked, it will call navigate

var navigate = function(event){

    event.preventDefault(); // stop the action

    var href = $(this).attr('href')

    // this = the HTML element which fired the event, in this case a click. We want the href attribute
    // because that is the link the person clicked on

    mainDiv.load(href + ' .yourMainDivClass') //

}


// if you want to add animate to this effect, you would
// 1. hide the div
// 2. load() the new content
// 3. add a callback function to the load() arguments
// which is triggered after the load is complete
// and in this callback function unhide div again