jQuery is a fast, small, and feature-rich JavaScript library. It simplifies tasks such as HTML document traversal and manipulation, event handling, animation, and Ajax interactions. jQuery provides an easy-to-use API that works across a multitude of browsers, making it easier to develop cross-browser compatible web applications. Its succinct syntax and powerful features allow developers to write less code and achieve more functionality. jQuery has been widely adopted for enhancing web pages with interactive elements and is often used in conjunction with other JavaScript frameworks and libraries.