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 include jQuery by linking to a CDN (Content Delivery Network) like this < script src="https://code.jquery.com/jquery-3.6.0.min.js">

It generally recommended to use the latest stable version, as it includes the most recent bug fixes and features. However, if you are working on legacy projects, you may need to use an older version compatible with the codebase.