Windows Presentation Foundation (WPF) is a framework for developing Windows applications introduced in .NET 3.0 that uses XAML as a declarative language. WPF supports superior data binding, animations through storyboarding, 3D graphics, and better performance through cleaner control usage. The WPF architecture includes XAML for designing GUIs with a logical and visual elements tree, layouts like stack panels and grids, dependency properties, routed events, and data binding. Templates, styles with triggers, resources, and user controls allow customizing appearances. Infragistics provides UI development tools and components that work with WPF for building line of business applications.