QTTabBar is a Shell-Extension to add Tab functionality to Windows Explorer - folder window.
Besides, QTTabBar provides various features that certainly help you deal with files and folders.

What can it do?

Most of the functionalities are activated when you enable the toolbars offered by QTTabBar in a folder window.

Tab Bar realizes ... the tabbed browsing of folders. Command Bars offer various command buttons including ones added by Plug-Ins. Extra Views show extra folder view in a folder window.

Once you enable them, QTTabBar installs some kind of hooks into the folder window and change the behavior of the Explorer to suit the need of advanced users.

For example, a new tab will be opened by middle-clicking on a folder icon. Preview tooltip is displayed when you point image, text, and movie file by mouse cursor. Do you want to mark an important file? Change the color of the name of it. When you move mouse cursor over folder icons, you'll see a square with blue arrow. Click and access to contents of the folder instantly!