AJAX Controls are user interface components that enhance web applications by allowing asynchronous data loading without refreshing the entire page. This means that when a user interacts with a control, such as a button or dropdown, only a portion of the web page updates, providing a smoother and more responsive experience. These controls are commonly used in frameworks like ASP.NET to simplify the development of dynamic web applications. They help developers create rich user experiences by managing data interactions seamlessly, improving performance and usability for end-users.