Document.ready() function is different from body onload() function because off 2 reasons.
1. We can have more than one document.ready() function in a page where we can have only one onload function.
2. Document.ready() function is called as soon as DOM is loaded where body.onload() function is called when everything gets loaded on the page that includes DOM, images and all associated resources of the page.
and you good to go now for JQuery.
Note : 1.3.2 denotes the library version.. It can be vary depending upon the version of Jquery you download.
JQuery UI is a library which is built on top of JQuery library. JQuery UI comes with cool widgets, effects and interaction mechanism.
See below page on this site. Date Picker control used in this page to select date is an example of JQuery UI.
Features of Jquery
1. One can easily provide effects and can do animations.
2. Applying / Changing CSS.
3. Cool plugins.
4. Ajax support
5. DOM selection events
6. Event Handling
Some of the common methods are :