Kendo UI is a JavaScript framework that provides 70+ UI widgets, charts, and mobile app tools. It includes everything needed for web and mobile development, such as an application framework, data visualization, and Angular integration. Developers can build responsive web and hybrid mobile apps using the same codebase. Key features include MVVM bindings, templates, and a data source for easy data handling. The framework is free and open source, with commercial offerings for additional widgets and server-side wrappers.