What is the jQuery UI library and how does it differ from core jQuery

jQuery UI is a set of user interface interactions, effects, widgets, and themes built on top of the core jQuery library. While jQuery focuses primarily on simplifying HTML document traversing, event handling, and AJAX interactions, jQuery UI provides additional features for building interactive web applications. It includes tools for creating sortable lists, datepickers, sliders, and more, making it easier for developers to build rich user experiences.