jQuery is a JavaScript library that simplifies common tasks like handling clicks, animating elements, and manipulating page content. It became hugely popular because it made JavaScript far easier and more consistent to work with across different browsers.
WordPress has included jQuery as part of its core software for years, which is why so many themes and plugins rely on it for interactive features like sliders, tabs, and pop-ups.
A Small Example
jQuery(".menu-toggle").on("click", function () {
jQuery(".main-menu").toggleClass("open");
});This snippet shows or hides a menu whenever a toggle button is clicked — a common pattern behind mobile navigation menus on many WordPress sites.
Is jQuery Still Relevant?
Modern JavaScript has made many of jQuery’s original conveniences unnecessary for new projects, and newer tools have largely taken its place in cutting-edge development. Still, because so much existing WordPress code depends on it, jQuery remains deeply embedded in the ecosystem and isn’t going away anytime soon.