Gtk X.x

[Tsarevich]

What is GTK? Can GTK X.X Themes be run on GNOME and XFCE?

Is XFCE considered faster than KDE and GNOME?

[daark.child]

GTK2 is the GUI toolkit used to build GNOME, XFCE and individual apps such as GIMP. You can use GTK2 themes in GNOME or XFCE, but some themes maybe designed specifically for XFCE or specifically for GNOME. Is XFCE faster than GNOME and KDE, for me yes.

[Cabhan]

Gtk is a widget toolkit. What this means is that it provides things like windows, buttons, textfields, etc. to allow developers to provide interfaces for their programs. Other widget toolkits include Qt, wxWidgets, Tk, and ncurses (for writing "GUIs" for the commandline).

While Gnome and Xfce are written using Gtk, you can still run non-Gtk apps in these environments. For instance, the popular CD-burning software k3b is developed in Qt. As a result, you can use Gtk themes, but k3b would be unaffected. In fact, you can apply Gtk themes anywhere, but they will only affect Gtk applications.

Gnome and Xfce are what are called desktop environments. Both provide a window manager, menus, toolbars, and a number of other applications. However, Gnome is an older project, and is somewhat heavier. One of Xfce's project goals is to write a somewhat lightweight desktop environment, and so on most systems it will run faster than Gnome. Of course, it does depend on what you're trying to do: rendering a movie would not, for instance, be noticeably faster.