Jquery is a library built on the Javascript scripting language. Basically what it does is take commonly used functions and package them into easy to use bits of code. For instance hiding or showing objects, changing CSS classes, adding in HTML content, changing HTML content and other things like this.
Hiding something using javascript alone looks like this
function showstuff(boxid){
document.getElementById(boxid).style.visibility="visible";
}
and is Jquery it looks like this
$('#boxid').hide();
There are also hundreds of plugins that will do almost anything you like.
cool eh?
Jquery UI is a collection of pre-made and highly customizable user interface elements, such as dialog boxes, date pickers, accordion collapsing lists, and lots more. Check out the demos for ideas. I’d recommend having a look while you are designing, as you might get some ideas. You can also do stuff like autocomplete form fields from a list of choices, make objects draggable and droppable, resizable, or sortable.