jQuery is a fast, small, and feature-rich JavaScript library that is designed to simplify client-side HTML scripting. It makes it easy to traverse HTML documents, manipulate DOM elements, handle events, and manage animations. jQuery is built on top of JavaScript, so it's compatible with all modern web browsers and easy to integrate into your projects.

One of the biggest benefits of using jQuery is that it simplifies the process of writing JavaScript code. It provides an extensive set of pre-written functions and methods that allow developers to write concise code while still achieving complex functionality. This not only saves time but also makes code more readable and easier to maintain.

jQuery also provides a range of plugins and UI widgets, which add additional functionality to your web application. These plugins allow developers to quickly create interactive components such as sliders, menus, and image galleries without having to write lots of code from scratch.

Overall, jQuery is a valuable tool for web developers of all levels, and its popularity is a testament to its ease of use and effectiveness.