- Windows Forms (WinForms)
- Windows Presentation Foundation (WPF)
WinForms use only native Windows interface elements - limited control on how things will look like.
With WPF you have full freedom of design but it's way more complicated than WinForms.
WPF is built on DirectX - this provide hardware acceleration and also enables modern UI features like transparency, gradients and transforms.
Also WPF offers a new markup language alternative - XAML - a different means of defining UI elements. An application that is defined as WPF is able to be deployed on the desktop or hosted on a webserver.
WinForms are events driven.