Projects
The jQuery Project manages all of the jQuery projects, including jQuery Core, jQuery UI, Sizzle and QUnit.
jQuery Core
jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript.
jQuery UI
jQuery UI provides abstractions for low-level interaction and animation, advanced effects and high-level, themeable widgets, built on top of the jQuery JavaScript Library, that you can use to build highly interactive web applications.
QUnit
QUnit is a powerful, easy-to-use, JavaScript test suite. It’s used by the jQuery project to test its code and plugins but is capable of testing any generic JavaScript code (and even capable of testing JavaScript code on the server-side).
Sizzle
A pure-JavaScript CSS selector engine designed to be easily dropped in to a host library.