XAML, or eXtensible Application Markup Language, is a markup language used primarily for designing user interfaces in applications built on the Microsoft .NET framework. It allows developers to create rich, interactive interfaces by defining the layout, appearance, and behavior of UI elements in a clear and structured way. XAML is often used in conjunction with WPF (Windows Presentation Foundation) and UWP (Universal Windows Platform) applications. By separating the UI design from the application logic, XAML enables a more organized development process, making it easier for designers and developers to collaborate on projects.