jQuery 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 various browsers.

You can explore the official jQuery documentation at api.jquery.com, which offers comprehensive information and examples for each feature of the library.

The $ is simply an alias for jQuery. Its a shortcut that allows you to type less code. For example, $() is the same as jQuery().