libgtk2

The gtk+ package contains the GIMP ToolKit (GTK+), a library for creating graphical user interfaces for the X Window System. GTK+ was originally written for the GIMP (GNU Image Manipulation Program) image processing program, but is now used by several other programs as well.

If you are planning on using the GIMP or another program that uses GTK+, you'll need to have the gtk+ package installed.