Explain the features provided by jQuery?

J Query is a fast, small, and feature-rich JavaScript library. It makes things like HTML document traversal and manipulation, event handling, animation, and Ajax much simpler with an easy to use API that works across a multitude of browsers.

• J Query UI is a curated set of user interface interactions,effects,widgets and themes built on top of the J Query
• J Query Mobile is a HTML5-based user interface system designed to make responsive web sites and apps that are accessible on all smart phone, tablet and desktop devices. 
•  QUnit is a powerful, easy-to-use Javacript unit testing framework, It's used by the JQuery UI and J Query Mobile projects and is capable of testing any generic JavaScript code.
• Sizzle is a pure-JavaScript CSS selector engine designed to be easily dropped in to a host library.