Enlightenment is a window manager for X. It's design goal is to be as configurable as possible - in look AND in feel. Currently in the look department it pretty much has that done. You can design your own window borders, menus, and other elements of your screen to look any way you like. Enlightenments current design aim is to become a desktop shell. That means it will manage your application windows, being able to launch applications, and also manage your files.