These are a pair of Windows shell extension which plugs into your OS and allows Windows to show a thumbnail of the VTF file when browsing in Thumbnail view, or info about the VTF file in columns in details view. The extension is a simple DLL which is installed into your system folder and registerd automatically - just run the installer.
IMPORTANT! Before you install the VTF Shell Extensions, you need to install the correct Visual Studio C++ Runtimes for you're operating system. Without the correct version the extensions will not work!