There are many articles about Windows Forms and WPF on this site—and they have been helpful to people for a long time. With Windows Forms and WPF developers can make Windows applications that have windows, buttons, dialog boxes, and C# or VB.NET code.
But as competing technologies like web browsers have become more powerful and widespread, Windows Forms and WPF have become less useful. It is possible to build a simple web server in nearly any language that serves HTML pages and handles input from clicks and POST requests. And web browsers have many advantages over WinForms and WPF:
For some applications that need native speed, like text editors, web browsers and even games, it is necessary to use native UI controls. But for the vast majority of applications that one might need, web browsers are probably a better platform to target. Of course, for older applications that have already been written, continuing to support Windows Forms and WPF is necessary.