Web forms cannot use the standard Windows controls. Instead, they use server controls, HTML controls, user controls, or custom controls created specially for Web forms.
Web applications are displayed in a browser. Windows applications display their own windows and have more control over how those windows are displayed.
Web forms are instantiated on the server, sent to the browser, and destroyed immediately. Windows forms are instantiated, exist for as long as needed, and are destroyed.
Web applications run on a server and are displayed remotely on clients. Windows applications run on the same machine they are displayed on.